Method and apparatus for supplying power in a local area network

ABSTRACT

A method for supplying power to a local area network node over communication cabling, the method comprising: injecting current-limited current into communication cabling connected to the local area network node; measuring a voltage developed in accordance with said injected current limited current across said communication cabling at three pre-determined intervals; and determining, as a consequence of said measured voltage at said three pre-determined intervals whether characteristics of the local area network node allow it to receive power over the communication cabling.

REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.10/218,739 filed Aug. 13, 2002 which is a continuation of U.S. patentapplication Ser. No. 09/365,584 filed Aug. 2, 1999 issued as U.S. Pat.No. 6,473,608, which claims priority from U.S. Provisional PatentApplication Ser. No. 60/115,628 filed Jan. 12, 1999 and is acontinuation-in-part of U.S. patent application Ser. No. 09/293,343filed Apr. 16, 1999 issued as U.S. Pat. No. 6,643,566. The entirecontent of each of the above mentioned applications and patents areincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to structured cabling systems and moreparticularly to structured cabling systems used in local area networkssupplying power to at least one node.

BACKGROUND OF THE INVENTION

Structured cabling systems are well known for use in institutionalinfrastructure. Such systems provide a standardized yet flexibleplatform for a dynamic communications environment. Typically structurecabling systems employ twisted copper pairs which are installed inaccordance with predetermined criteria. Structured cabling systems areconventionally employed for telephone, data communications, as well asfor alarms, security and access control applications.

SUMMARY OF THE INVENTION

The present invention seeks to provide an enhanced structured cablingsystem and local area network employing such a system.

There is thus provided in accordance with a preferred embodiment of thepresent invention a local area network including a hub, a plurality ofnodes, communication cabling connecting the plurality of nodes to thehub for providing data communication; and a power supply distributoroperative to provide at least some operating power to at least some ofthe plurality of nodes via the communication cabling.

Further in accordance with a preferred embodiment of the presentinvention the communication cabling includes at least part of astructured cabling system.

Still further in accordance with a preferred embodiment of the presentinvention the power supply distributor is located within the hub.

Additionally in accordance with a preferred embodiment of the presentinvention the power supply distributor is located outside the hub.

Moreover in accordance with a preferred embodiment of the presentinvention the power supply distributor is located partially within thehub and partially outside the hub.

Still further in accordance with a preferred embodiment of the presentinvention the operating power supplied by said power supply distributorto at least some of said plurality nodes via said communication cablingincludes backup power.

Additionally in accordance with a preferred embodiment of the presentinvention the hub includes a data communication concentrator, the powersupply distributor includes a combiner, and the communication cablingconnects the data communication concentrator via the combiner to thenodes.

Sill further in accordance with a preferred embodiment of the presentinvention the hub includes a data communication concentrator and whereinthe power supply distributor is also located within the hub.

Additionally in accordance with a preferred embodiment of the presentinvention the hub includes a data communication concentrator and whereinthe power supply distributor is also located within the hub and includesa power supply and a combiner, the combiner coupling power from thepower supply to the communication cabling which also carries data fromthe data communication concentrator.

Preferably the data communication concentrator comprises a LAN switchwhich functions as a data communication switch/repeater.

Additionally in accordance with a preferred embodiment of the presentinvention the plurality of nodes includes at least one of the followingtypes of nodes: wireless LAN access points, emergency lighting systemelements, paging loudspeakers, CCTV cameras, alarm sensors, door entrysensors, access control units, laptop computers, IP telephones, hubs,switches, routers, monitors and memory backup units for PCs andworkstations.

Still further in accordance with a preferred embodiment of the presentinvention the hub includes a data communication concentrator the powersupply distributor includes a combiner and a power supply, thecommunication cabling connects the data communication concentrator viathe combiner to the nodes, and the combiner includes a plurality ofcouplers, each of which is connected to an output of the power supply.

Further in accordance with a preferred embodiment of the presentinvention the hub includes a data communication concentrator, the powersupply distributor includes a combiner and a power supply, thecommunication cabling connects the data communication concentrator viathe combiner to the nodes, and the combiner comprises a plurality ofcouplers and a plurality of filters, each coupler being connected via afilter to an output of the power supply.

Still further according to a preferred embodiment of the presentinvention the hub includes a data communication concentrator, the powersupply distributor includes a combiner and a power supply, thecommunication cabling connects the data communication concentrator viathe combiner to the nodes, and the combiner includes a plurality ofcouplers and a plurality of filters and a plurality of smart powerallocation and reporting circuits (SPEARs), each coupler being connectedvia a filter and a SPEAR to an output of the power supply.

Moreover in accordance with a preferred embodiment of the presentinvention the hub includes a data communication concentrator, the powersupply distributor includes a combiner and a power supply, and the powersupply includes a power failure backup facility.

Additionally or alternatively the hub includes a data communicationconcentrator; the power supply distributor includes a combiner and apower supply, the communication cabling connects the data communicationconcentrator via the combiner to the nodes, and the combiner comprises aplurality of couplers and a plurality of filters, each coupler beingconnected via a filter to an output of the power supply.

Moreover according to a preferred embodiment of the present inventionthe hub includes a data communication concentrator, the power supplydistributor includes a combiner and a power supply, the communicationcabling connects the data communication concentrator via the combiner tothe nodes, and the combiner includes a plurality of couplers and aplurality of filters and a plurality of smart power allocation andreporting circuits (SPEARs), each coupler being connected via a filterand a SPEAR to an output of the power supply.

Preferably the hub includes a data communication concentrator, the powersupply distributor includes a combiner and a power supply, thecommunication cabling connects the data communication concentrator viathe combiner to the nodes, and the combiner includes a plurality ofcouplers and a plurality of filters, each coupler being connected via afilter to an output of the power supply.

Additionally or alternatively the hub includes a data communicationconcentrator, the power supply distributor includes a combiner and apower supply, the communication cabling connects the data communicationconcentrator via the combiner to the nodes, and the combiner comprises aplurality of couplers and a plurality of filters and a plurality ofsmart power allocation and reporting circuits (SPEARs), each couplerbeing connected via a filter and a SPEAR to an output of the powersupply.

Preferably the hub includes a data communication concentrator, the powersupply distributor includes a combiner and a power supply, thecommunication cabling connects the data communication concentrator viathe combiner to the nodes, and the combiner includes a plurality ofcouplers and a plurality of filters, each coupler being connected via afilter to an output of the power supply.

Additionally or alternatively the hub includes a data communicationconcentrator, the power supply distributor includes a combiner and apower supply, the communication cabling connects the data communicationconcentrator via the combiner to the nodes, and the combiner includes aplurality of couplers and a plurality of filters and a plurality ofsmart power allocation and reporting circuits (SPEARs), each couplerbeing connected via a filter and a SPEAR to an output of the powersupply.

Further in accordance with a preferred embodiment of the presentinvention the power supply distributor is operative to provideelectrical power along the communication cabling without unacceptabledegradation of the digital communication.

Still further in accordance with a preferred embodiment of the presentinvention the communication cabling comprises at least one twisted wirepair connected to each node and wherein power is transmitted over atwisted wire pair along which data is also transmitted.

Preferably the hub includes a data communication concentrator, the powersupply distributor includes a power supply interface and a power supply,the communication cabling connects the data communication concentratorvia the power supply interface to the nodes, and power supply interfaceincludes a plurality of filters and a plurality of smart powerallocation and reporting circuits (SPEARs), each filter being connectedvia a SPEAR to an output of the power supply.

Additionally in accordance with a preferred embodiment of the presentinvention the communication cabling comprises at least two twisted wirepairs connected to each node and wherein power is transmitted over atwisted wire pair different from that along which data is transmitted.

Preferably the hub includes a data communication concentrator, the powersupply distributor includes a power supply interface and a power supply,the communication cabling connects the data communication concentratorvia the power supply interface to the nodes, and the power supplyinterface includes a plurality of filters and a plurality of smart powerallocation and reporting circuits (SPEARs), each filter being connectedvia a SPEAR to an output of the power supply.

Still further in accordance with a preferred embodiment of the presentinvention the hub includes a data communication concentrator, the powersupply distributor includes a combiner and a power supply, thecommunication cabling connects the data communication concentrator viathe combiner to the nodes, the combiner includes a plurality of couplersand a plurality of filters and a plurality of smart power allocation andreporting circuits (SPEARs), each coupler being connected via a filterand a SPEAR to an output of the power supply, and each coupler has atleast two ports, one of which is connected to a port of the datacommunication concentrator and the other of which is connected, viacommunication cabling, to one of the plurality of nodes.

There is also provided in accordance with a preferred embodiment of thepresent invention a local area network node for use in a local areanetwork including a hub, a plurality of nodes, communication cablingconnecting the plurality of nodes to the hub for providing digitalcommunication and a power supply distributor operative to provide atleast some operating power to at least some of the plurality of nodesvia the hub and the communication cabling, the local area network nodeincluding a communications cabling interface receiving both power anddata and separately providing power to a node power input and data to anode data input.

Further in accordance with a preferred embodiment of the presentinvention the communications cabling interface is internal to at leastone of the plurality of nodes.

Still further in accordance with a preferred embodiment of the presentinvention the communications cabling interface is external to at leastone of the plurality of nodes.

Additionally in accordance with a preferred embodiment of the presentinvention the power supply distributor is operative to provideelectrical power along the communication cabling without unacceptabledegradation of the digital communication.

Still further in accordance with a preferred embodiment of the presentinvention the communication cabling includes at least one twisted wirepair connected to each node and wherein power is transmitted over atwisted wire pair along which data is also transmitted.

Additionally in accordance with a preferred embodiment of the presentinvention the communication cabling includes at least two twisted wirepairs connected to each node and wherein power is transmitted over atwisted wire pair different from that along which data is transmitted.

Preferably the power supply distributor is operative to provideelectrical power along the communication cabling without unacceptabledegradation of the digital communication.

Additionally the communication cabling may include at least one twistedwire pair connected to each node and wherein power is transmitted over atwisted wire pair along which data is also transmitted.

Further more in accordance with a preferred embodiment of the presentinvention the communication cabling includes at least two twisted wirepairs connected to each node and wherein power is transmitted over atwisted wire pair different from that along which data is transmitted.

Preferably the power supply distributor is operative to provideelectrical power along the communication cabling without unacceptabledegradation of the digital communication.

Further in accordance with a preferred embodiment of the presentinvention the communication cabling includes at least one twisted wirepair connected to each node and wherein power is transmitted over atwisted wire pair along which data is also transmitted.

Still further in accordance with a preferred embodiment of the presentinvention the communication cabling includes at least two twisted wirepairs connected to each node and wherein power is transmitted over atwisted wire pair different from that along which data is transmitted.

Moreover in accordance with a preferred embodiment of the presentinvention the hub includes a data communication concentrator, the powersupply distributor includes a combiner, a management and control unitand a power supply, the communication cabling connects said datacommunication concentrator via the combiner to the node, the combinerincludes a plurality of couplers and a plurality of filters and aplurality of smart power allocation and reporting circuits (SPEARs),each coupler being connected via a filter and a SPEAR to an output ofsaid power supply, and the SPEAR is operative to report to themanagement and control unit the current consumption of a node connectedthereto.

Further in accordance with a preferred embodiment of the presentinvention the hub includes a data communication concentrator, the powersupply distributor includes a combiner and a power supply, thecommunication cabling connects the data communication concentrator viathe combiner to the nodes, the combiner comprises a plurality ofcouplers and a plurality of filters and a plurality of smart powerallocation and reporting circuits (SPEARs), each coupler being connectedvia a filter and a SPEAR to an output of the power supply, and the SPEARis operative to limit the maximum current supplied to a node connectedthereto.

Alternatively according to a preferred embodiment of the presentinvention the hub includes a data communication concentrator, the powersupply distributor includes a combiner and a power supply, thecommunication cabling connects the data communication concentrator viathe combiner to the nodes, the combiner includes a plurality of couplersand a plurality of filters and a plurality of smart power allocation andreporting circuits (SPEARs), each coupler being connected via a filterand a SPEAR to an output of the power supply, and the SPEAR is operativeto automatically disconnect a node connected thereto displaying anovercurrent condition following elapse of a programmably predeterminedperiod of time.

Additionally in accordance with a preferred embodiment of the presentinvention the hub includes a data communication concentrator, the powersupply distributor includes a combiner and a power supply, thecommunication cabling connects the data communication concentrator viathe combiner to the nodes, the combiner includes a plurality of couplersand a plurality of filters and a plurality of smart power allocation andreporting circuits (SPEARs), each coupler being connected via a filterand a SPEAR to an output of the power supply, and the SPEAR is operativeto automatically disconnect power from a node connected theretodisplaying an overcurrent condition following elapse of a programmablypredetermined period of time and to automatically reconnect the node topower thereafter when it no longer displays the overcurrent condition.

Moreover in accordance with a preferred embodiment of the presentinvention the hub includes a data communication concentrator, the powersupply distributor includes a combiner and a power supply, thecommunication cabling connects said data communication concentrator viathe combiner to the nodes, the combiner includes a plurality of couplersand a plurality of filters and a plurality of smart power allocation andreporting circuits (SPEARs), each coupler being connected via a filterand a SPEAR to an output of the power supply, and the SPEAR includes acurrent sensor which receives a voltage input Vin from a power supplyand generates a signal which is proportional to the current passingtherethrough, and a multiplicity of comparators receiving the signalfrom the current sensor and also receiving a reference voltage Vref fromrespective reference voltage sources.

Preferably the reference voltage sources are programmable referencevoltage sources and receive control inputs from management & controlcircuits.

Additionally the outputs of the multiplicity of comparators may besupplied to a current limiter and switch which receives input voltageVin via the current sensor and provides a current-limited voltage outputVout.

Furthermore the outputs of the comparators are supplied to management &control circuits to serve as monitoring inputs providing informationregarding the DC current flowing through the SPEAR.

Additionally in accordance with a preferred embodiment of the presentinvention the hub includes a data communication concentrator, the powersupply distributor includes a combiner and a power supply, thecommunication cabling connects the data communication concentrator viathe combiner to the nodes, and the combiner includes a plurality ofcouplers each of which includes at least a pair of transformers, eachhaving a center tap at a secondary thereof via which the DC voltage isfed to each wire of a twisted pair connected thereto.

Further in accordance with a preferred embodiment of the presentinvention the hub includes a data communication concentrator, the powersupply distributor includes a combiner and a power supply, thecommunication cabling connects the data communication concentrator viathe combiner to the nodes, and the combiner includes a plurality ofcouplers each of which includes at least one transformer, which ischaracterized in that it includes a secondary which is split into twoseparate windings and a capacitor which is connected between the twoseparate windings and which effectively connects the two windings inseries for high frequency signals, but effectively isolates the twowindings for DC.

Still further in accordance with a preferred embodiment of the presentinvention the hub includes a data communication concentrator, the powersupply distributor includes a combiner a power supply, the communicationcabling connects the data communication concentrator via the combiner tothe nodes, and the combiner includes a pair of capacitors whicheffectively block DC from reaching the data communication concentrator.

Still further in accordance with a preferred embodiment of the presentinvention the hub includes a data communication concentrator, the powersupply distributor includes a combiner and a power supply, thecommunication cabling connects the data communication concentrator viathe combiner to the nodes, and the combiner comprises two pairs ofcapacitors which effectively block DC from reaching the datacommunication concentrator.

Additionally in accordance with a preferred embodiment of the presentinvention the hub includes a data communication concentrator, the powersupply distributor includes a combiner and a power supply, thecommunication cabling connects the data communication concentrator viathe combiner to the nodes, and the combiner includes a self-balancingcapacitor-less and transformer-less common mode coupling circuit.

Preferably the communications cabling interface includes a separator anda pair of transformers, each having a center tap at a primary thereofvia which the DC voltage is extracted from each wire of a twisted pairconnected thereto.

Additionally or alternatively the communications cabling interfaceincludes a separator including at least one transformer, which ischaracterized in that it includes a primary which is split into twoseparate windings and a capacitor which is connected between the twoseparate windings and which effectively connects the two windings inseries for high frequency signals, but effectively isolates the twowindings for DC.

Furthermore the communications cabling interface includes a separatorcomprising a pair of capacitors which effectively block DC from reachinga data input of a node connected thereto.

Additionally in accordance with a preferred embodiment of the presentinvention the communications cabling interface includes a separatorcomprising two pairs of capacitors which effectively block DC fromreaching a data input of a node connected thereto.

Additionally or alternatively the communications cabling interfaceincludes a separator includes a self-balancing capacitor-less andtransformer-less common mode coupling circuit.

There is further provided in accordance with a preferred embodiment ofthe present invention a local area network including a hub, a pluralityof nodes, a communication cabling connecting said plurality of nodes tothe hub for providing data communication, and a power supply distributoroperative to provide at least some operating power to at least some ofthe plurality of nodes via the communication cabling, the power supplydistributor including power management functionality.

Preferably the power supply distributor includes a power management &control unit which monitors and controls the power supplied to variousnodes via the communications cabling.

Additionally in accordance with a preferred embodiment of the presentinvention the power supply distributor includes a management workstationwhich is operative to govern the operation of the power management &control unit.

Preferably the management workstation governs the operation of multiplepower management & control units.

Moreover in accordance with a preferred embodiment of the presentinvention the power management & control unit communicates with variousnodes via a data communication concentrator thereby to govern theircurrent mode of power usage.

Further in accordance with a preferred embodiment of the presentinvention the power management & control unit communicates with variousnodes via control messages which are decoded at the nodes and areemployed for controlling whether full or partial functionality isprovided thereat.

Still further in accordance with a preferred embodiment of the presentinvention the power management & control unit senses that mains power tosaid power supply distributor is not available and sends a controlmessage to cause nodes to operate in a backup or reduced power mode.

Preferably the node includes essential circuitry, which is required forboth full functionality and reduced functionality operation, andnon-essential circuitry, which is not required for reduced functionalityoperation.

There is also provided with yet another preferred embodiment of thepresent invention a local area network power supply distributor for usein a local area network including a hub, a plurality of nodes andcommunication cabling connecting the plurality of nodes to a hub forproviding digital communication therebetween, the power supplydistributor being operative to provide at least some operating power toat least some of said plurality of nodes via the communication cabling.

Further in accordance with a preferred embodiment of the presentinvention the supply distributor is located within the hub.

Still further in accordance with a preferred embodiment of the presentinvention the power supply distributor is located outside the hub.Alternatively the power supply distributor is located partially withinthe hub and partially outside the hub.

Additionally in accordance with a preferred embodiment of the presentinvention the operating power supplied by the power supply distributorto at least some of the plurality nodes via the communication cablingincludes backup power.

Still further in accordance with a preferred embodiment of the presentinvention the hub includes a data communication concentrator, the powersupply distributor includes a combiner, and the communication cablingconnects the data communication concentrator via the combiner to thenodes.

Moreover in accordance with a preferred embodiment of the presentinvention the hub includes a data communication concentrator and whereinthe power supply distributor is also located within the hub.

Still further in accordance with a preferred embodiment of the presentinvention the hub includes a data communication concentrator and whereinsaid power supply distributor is also located within the hub andincludes a power supply and a combiner, the combiner coupling power fromthe power supply to the communication cabling which also carries datafrom the data communication concentrator.

Preferably the combiner includes a plurality of couplers, each of whichis connected to an output of the power supply.

Additionally in accordance with a preferred embodiment of the presentinvention the combiner includes a plurality of couplers and a pluralityof filters, each coupler being connected via a filter to an output ofthe power supply.

Furthermore the combiner may also include a plurality of couplers and aplurality of filters and a plurality of smart power allocation andreporting circuits (SPEARs), each coupler being connected via a filterand a SPEAR to an output of the power supply.

Additionally in accordance with a preferred embodiment of the presentinvention the power supply distributor includes a power supply, and thepower supply includes a power failure backup facility.

Still further in accordance with a preferred embodiment of the presentinvention the combiner includes a plurality of couplers and a pluralityof filters, each coupler being connected via a filter to an output ofthe power supply.

Preferably the combiner includes a plurality of couplers and a pluralityof filters and a plurality of smart power allocation and reportingcircuits (SPEARs), each coupler being connected via a filter and a SPEARto an output of the power supply.

Moreover in accordance with a preferred embodiment of the presentinvention the combiner includes a plurality of couplers and a pluralityof filters, each coupler being connected via a filter to an output of apower supply.

Additionally the combiner may also include a plurality of couplers and aplurality of filters and a plurality of smart power allocation andreporting circuits (SPEARs), each coupler being connected via a filterand a SPEAR to an output of the power supply.

Furthermore the combiner may also include a plurality of couplers and aplurality of filters, each coupler being connected via a filter to anoutput of a power supply.

Moreover in accordance with a preferred embodiment of the presentinvention the power supply distributor is operative to provideelectrical power along the communication cabling without unacceptabledegradation of the digital communication.

Further in accordance with a preferred embodiment of the presentinvention the communication cabling includes at least one twisted wirepair connected to each node and wherein power is transmitted over atwisted wire pair along which data is also transmitted.

Preferably the power supply distributor includes a power supplyinterface and a power supply, the communication cabling connects thedata communication concentrator via the power supply interface to thenodes, and the power supply interface includes a plurality of filtersand a plurality of smart power allocation and reporting circuits(SPEARs), each filter being connected via a SPEAR to an output of thepower supply.

Additionally in accordance with a preferred embodiment of the presentinvention the communication cabling includes at least two twisted wirepairs connected to each node and wherein power is transmitted over atwisted wire pair different from that along which data is transmitted.

Moreover in accordance with a preferred embodiment of the presentinvention the hub includes a data communication concentrator, the powersupply distributor includes a power supply interface and a power supply,the communication cabling connects the data communication concentratorvia the power supply interface to said nodes, and the power supplyinterface includes a plurality of filters and a plurality of smart powerallocation and reporting circuits (SPEARs), each filter being connectedvia a SPEAR to an output of the power supply.

Still further in accordance with a preferred embodiment of the presentinvention the hub includes a data communication concentrator, the powersupply distributor includes a combiner and a power supply, thecommunication cabling connects the data communication concentrator viathe combiner to the nodes, the combiner includes a plurality of couplersand a plurality of filters and a plurality of smart power allocation andreporting circuits (SPEARs), each coupler being connected via a filterand a SPEAR to an output of the power supply, and each coupler has atleast two ports, one of which is connected to a port of the datacommunication concentrator and the other of which is connected, viacommunication cabling, to one of the plurality of nodes.

Additionally in accordance with a preferred embodiment of the presentinvention the hub includes a data communication concentrator, the powersupply distributor includes a combiner, a management and control unitand a power supply, the communication cabling connects said datacommunication concentrator via the combiner to the nodes, the combinerincludes a plurality of couplers and a plurality of filters and aplurality of smart power allocation and reporting circuits (SPEARs),each coupler being connected via a filter and a SPEAR to an output ofthe power supply, and the SPEAR is operative to report to the managementand control unit the current consumption of a node connected thereto.

Still further in accordance with a preferred embodiment of the presentinvention the hub includes a data communication concentrator, the powersupply distributor includes a combiner and a power supply, thecommunication cabling connects the data communication concentrator viathe combiner to the nodes, the combiner includes a plurality of couplersand a plurality of filters and a plurality of smart power allocation andreporting circuits (SPEARs), each coupler being connected via a filterand a SPEAR to an output of the power supply, and the SPEAR is operativeto limit the maximum current supplied to a node connected thereto.

Still further in accordance with a preferred embodiment of the presentinvention the hub includes a data communication concentrator, the powersupply distributor includes a combiner and a power supply, thecommunication cabling connects the data communication concentrator viathe combiner to the nodes, the combiner includes a plurality of couplersand a plurality of filters and a plurality of smart power allocation andreporting circuits (SPEARs), each coupler being connected via a filterand a SPEAR to an output of the power supply, and the SPEAR is operativeto automatically disconnect a node connected thereto displaying anovercurrent condition following elapse of a programmably predeterminedperiod of time.

Additionally in accordance with a preferred embodiment of the presentinvention the hub includes a data communication concentrator, the powersupply distributor includes a combiner and a power supply, thecommunication cabling connects the data communication concentrator viathe combiner to the nodes, the combiner includes a plurality of couplersand a plurality of filters and a plurality of smart power allocation andreporting circuits (SPEARs), each coupler being connected via a filterand a SPEAR to an output of the power supply, and the SPEAR is operativeto automatically disconnect power from a node connected theretodisplaying an overcurrent condition following elapse of a programmablypredetermined period of time and to automatically reconnect the node topower thereafter when it no longer displays the overcurrent condition.

Still further in accordance with a preferred embodiment of the presentinvention the hub includes a data communication concentrator, the powersupply distributor includes a combiner and a power supply, thecommunication cabling connects the data communication concentrator viathe combiner to the nodes, the combiner includes a plurality of couplersand a plurality of filters and a plurality of smart power allocation andreporting circuits (SPEARs), each coupler being connected via a filterand a SPEAR to an output of the power supply, and the SPEAR includes acurrent sensor which receives a voltage input Vin from a power supplyand generates a signal which is proportional to the current passingtherethrough, and a multiplicity of comparators receiving the signalfrom the current sensor and also receiving a reference voltage Vref fromrespective reference voltage sources.

Preferably the reference voltage sources are programmable referencevoltage sources and receive control inputs from management & controlcircuits.

Additionally the outputs of the multiplicity of comparators may besupplied to a current limiter and switch which receives input voltageVin via the current sensor and provides a current-limited voltage outputVout.

Furthermore the outputs of the comparators may be supplied to management& control circuits to serve as monitoring inputs providing informationregarding the DC current flowing through the SPEAR.

Still further in accordance with a preferred embodiment of the presentinvention the hub includes a data communication concentrator, the powersupply distributor includes a combiner and a power supply, thecommunication cabling connects the data communication concentrator viathe combiner to the nodes, and the combiner includes plurality ofcouplers each of which includes at least a pair of transformers, eachhaving a center tap at a secondary thereof via which the DC voltage isfed to each wire of a twisted pair connected thereto.

Additionally in accordance with a preferred embodiment of the presentinvention the hub includes a data communication concentrator, the powersupply distributor includes a combiner and a power supply, thecommunication cabling connects the data communication concentrator viathe combiner to the nodes, and the combiner includes a plurality ofcouplers each of which includes at least one transformer, which ischaracterized in that it includes a secondary which is split into twoseparate windings and a capacitor which is connected between the twoseparate windings and which effectively connects the two windings inseries for high frequency signals, but effectively isolates the twowindings for DC.

Further in accordance with a preferred embodiment of the presentinvention the hub includes a data communication concentrator, the powersupply distributor includes a combiner and a power supply, thecommunication cabling connects the data communication concentrator viathe combiner to the nodes, and the combiner includes a pair ofcapacitors which effectively block DC from reaching the datacommunication concentrator.

Still further in accordance with a preferred embodiment of the presentinvention the hub includes a data communication concentrator, the powersupply distributor includes a combiner and a power supply, thecommunication cabling connects the data communication concentrator viathe combiner to the nodes, and the combiner comprises two pairs ofcapacitors which effectively block DC from reaching the datacommunication concentrator.

Additionally in accordance with a preferred embodiment of the presentinvention the hub includes a data communication concentrator, the powersupply distributor includes a combiner and a power supply, thecommunication cabling connects the data communication concentrator viathe combiner to the nodes, and the combiner comprises a self-balancingcapacitor-less and transformer-less common mode coupling circuit.

Preferably the power supply distributor includes power managementfunctionality.

Additionally the power supply distributor may include a power management& control unit which monitors and controls the power supplied to variousnodes via the communications cabling.

Furthermore the power supply distributor may include a managementworkstation which is operative to govern the operation of said powermanagement & control unit.

Furthermore in accordance with a preferred embodiment of the presentinvention the management workstation governs the operation of multiplepower management & control units.

Preferably the power management & control unit communicates with variousnodes via a data communication concentrator thereby to govern theircurrent mode of power usage.

Additionally in accordance with a preferred embodiment of the presentinvention the power management & control unit communicates with variousnodes via control messages which are decoded at the nodes and areemployed for controlling whether full or partial functionality isprovided thereat.

Additionally the power management & control unit senses that mains powerto the power supply distributor is not available and sends a controlmessage to cause nodes to operate in a backup or reduced power mode.

Furthermore the node includes essential circuitry, which is required forboth full functionality and reduced functionality operation, andnon-essential circuitry, which is not required for reduced functionalityoperation.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood and appreciated more fully fromthe following detailed description, taken in conjunction with thedrawings in which:

FIGS. 1A and 1B are simplified block diagram illustrations of twoalternative embodiments of a local area network including a power supplyoperative to provide electrical power to local area network nodes overcommunication cabling constructed and operative in accordance with onepreferred embodiment of the present invention;

FIGS. 2A and 2B are simplified block diagram illustrations of twoalternative embodiments of a local area network including a power supplyoperative to provide electrical power to local area network nodes overcommunication cabling constructed and operative in accordance withanother preferred embodiment of the present invention;

FIGS. 3A & 3B are simplified block diagrams of hubs useful in theembodiments of FIGS. 1A and 1B respectively;

FIGS. 4A & 4B are simplified block diagrams of hubs and power supplysubsystems useful in the embodiments of FIGS. 2A & 2B respectively;

FIG. 5 is a simplified block diagram illustration of a smart powerallocation and reporting circuit useful in the embodiments of FIGS. 3A,3B, 4A and 4B;

FIG. 6 is a simplified schematic illustration of the embodiment of FIG.5;

FIGS. 7A & 7B are simplified block diagram illustrations of LAN nodeinterface circuits useful in the embodiments of FIGS. 1A & 2A and FIGS.1B & 2B respectively;

FIGS. 8A-8G are simplified block diagram and schematic illustrations ofvarious embodiments of a combiner useful in the embodiments of FIGS. 3Aand 4A;

FIGS. 9A-9G are simplified block diagram and schematic illustrations ofvarious embodiments of a separator useful in the embodiments of FIGS.1A, 2A & 7A in combination with combiners of FIGS. 8A-8G;

FIGS. 10A & 10B are simplified block diagram illustrations of twoalternative embodiments of a communications network including powersupply and management over communications cabling constructed andoperative in accordance with a preferred embodiment of the presentinvention;

FIGS. 11A & 111B are simplified block diagram illustrations of twoalternative embodiments of a local area network including power supplyand management unit operative to provide electrical power to local areanetwork nodes over communication cabling;

FIGS. 12A & 12B are simplified block diagram illustrations of a hubuseful in the embodiments of FIGS. 10A & 10B respectively;

FIGS. 13A & 13B are simplified block diagram illustrations of a hub anda power supply and management subsystem useful in the embodiments ofFIG. 11A & 11B respectively;

FIGS. 14A & 14B are simplified block diagrams of two different nodeconfigurations useful in the embodiments of FIGS. 10A, 10B, 11A & 11B;

FIG. 15 is a simplified block diagram of a node configuration whichcombines the features shown in FIGS. 14A & 14B;

FIG. 16 is a generalized flowchart illustrating power management in bothnormal operation and reduced power modes of the networks of FIGS. 10A,110B, 11A & 11B;

FIG. 17 is a generalized flowchart illustrating one step in theflowchart of FIG. 16;

FIGS. 18A and 18B together are a generalized flowchart illustrating apreferred embodiment of the interrogation and initial power supplyfunctionality which appears in FIG. 17;

FIGS. 19A, 19B, 19C and 19D are generalized flowcharts each illustratingone possible mechanism for full or no functionality operation in aninvoluntary power management step in the flowchart of FIG. 16;

FIGS. 20A, 20B, 20C and 20D are generalized flowcharts each illustratingone possible mechanism for full or reduced functionality operation in aninvoluntary power management step in the flowchart of FIG. 16;

FIGS. 21A, 21B, 21C and 21D are generalized flowcharts each illustratingone possible mechanism for node initiated sleep mode operation in avoluntary power management step in the flowchart of FIG. 16;

FIGS. 22A, 22B, 22C and 22D are generalized flowcharts each illustratingone possible mechanism for hub initiated sleep mode operation in avoluntary power management step in the flowchart of FIG. 16;

FIGS. 23A, 23B, 23C and 23D are generalized flowcharts each illustratingone possible mechanism for full or no functionality prioritizedoperation in a voluntary power management step in the flowchart of FIG.16; and

FIGS. 24A, 24B, 24C and 24D are generalized flowcharts each illustratingone possible mechanism for full or reduced functionality prioritizedoperation in a voluntary power management step in the flowchart of FIG.16.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Reference is now made to FIG. 1A, which is a simplified block diagramillustration of a local area network constructed and operative inaccordance with a preferred embodiment of the present invention. As seenin FIG. 1A, there is provided a local area network (LAN) comprising ahub 10 which is coupled, by cabling 11, preferably a structured cablingsystem, to a plurality of LAN nodes, such as a desktop computer 12, aweb camera 14, a facsimile machine 16, a LAN telephone, also known as anIP telephone 18, a computer 20 and a server 22.

Cabling 11 is preferably conventional LAN cabling having four pairs oftwisted copper wires cabled together under a common jacket. In theembodiment of FIG. 1A, as will be described hereinbelow, at least one ofthe pairs of twisted copper wires is employed for transmitting both dataand electrical power to nodes of the network. Typically two such pairsare employed for transmitting both data and electrical power along eachline connecting a hub to each node, while one such pair carries dataonly and a fourth pair is maintained as a spare and carries neither datanor power.

In accordance with a preferred embodiment of the present invention thereis provided a power supply subsystem 30 which is operative to provide atleast some operating or backup power to at least some of said pluralityof nodes via the hub 10 and the communication cabling connecting the hubto various LAN nodes.

In the illustrated embodiment of FIG. 1A, subsystem 30 is located withinthe hub 10 and includes a power supply 32 which supplies operating powerand/or backup power to various LAN nodes via the communication cabling.The communication cabling connects a LAN switch 34 via a combiner 36 tothe various LAN nodes. The combiner couples electrical power from thepower supply 32 along the communication cabling to at least some of theLAN nodes. Bidirectional data communications from LAN switch 34 passthrough the combiner 36, substantially without interference.

It is seen that the communication cabling 11 from the hub 10 to thedesktop computer 12, facsimile machine 16 and computer 20 carries bothdata and backup power, while the communication cabling from the hub 10to the hub camera 14 and LAN telephone 18 carries both data andoperating power and the communication cabling from the hub to the server22 carries only data, in a typically LAN arrangement constructed andoperative in accordance with a preferred embodiment of the presentinvention.

It is a particular feature of the embodiment of FIG. 1A that both dataand power are carried on the same twisted copper pair.

It is appreciated that each of the LAN nodes 12-20 which receives powerover the communication cabling includes a separator for separating theelectrical power from the data. In the illustrated embodiment of FIG.1A, the separators are typically internal to the respective nodes andare not separately designated, it being appreciated that alternativelydiscrete separators may be employed.

Reference is now made to FIG. 1B, which is a simplified block diagramillustration of a local area network constructed and operative inaccordance with another preferred embodiment of the present invention.As seen in FIG. 1B, there is provided a local area network (LAN)comprising a hub 60 which is coupled, by cabling 61, preferably astructured cabling system, to a plurality of LAN nodes, such as adesktop computer 62, a web camera 64, a facsimile machine 66, a LANtelephone, also known as an IP telephone 68, a computer 70 and a server72.

Cabling 61 is preferably conventional LAN cabling having four pairs oftwisted copper wires cabled together under a common jacket. In theembodiment of FIG. 1B, in contrast to the arrangement described abovewith respect to FIG. 1A and as will be described hereinbelow, at leastone of the pairs of twisted copper wires is employed only fortransmitting electrical power to nodes of the network and at least oneof the pairs of twisted copper wires is employed only for transmittingdata. Typically two such pairs are employed for transmitting data onlyand two such pairs are employed only for supplying electrical poweralong each line connecting a hub to each node.

In accordance with a preferred embodiment of the present invention thereis provided a power supply subsystem 80 which is operative to provide atleast some operating or backup power to at least some of said pluralityof nodes via the hub 60 and the communication cabling 61 connecting thehub to various LAN nodes.

In the illustrated embodiment of FIG. 1B, subsystem 80 is located withinthe hub 60 and includes a power supply 82 which supplies operating powerand/or backup power to various LAN nodes via the communication cabling.The communication cabling connects a LAN switch 84 via a power supplyinterface 86 to the various LAN nodes. The power supply interface 86distributes electrical power from the power supply 82, along twistedpairs of the communication cabling 61 which are not used for carryingdata, to at least some of the LAN nodes. Bidirectional datacommunications from LAN switch 84 pass through the power supplyinterface 86, substantially without interference.

It is seen that the communication cabling 61 from the hub 60 to thedesktop computer 62, facsimile machine 66 and computer 70 carries bothdata and backup power along separate twisted pairs, while thecommunication cabling 61 from the hub 60 to the hub camera 64 and LANtelephone 68 carries both data and operating power along separatetwisted pairs and the communication cabling 61 from the hub 60 to theserver 72 carries only data, in a typically LAN arrangement constructedand operative in accordance with a preferred embodiment of the presentinvention.

It is a particular feature of the embodiment of FIG. 1B that data andpower are carried on separate twisted copper pairs of each communicationcabling line.

It is appreciated that each of the LAN nodes 62-70 which receives powerover the communication cabling 61 includes a connector for connectingthe twisted pairs carrying electrical power to a node power supply andseparately connecting the twisted pairs carrying data to a data input ofthe node. In the illustrated embodiment of FIG. 1B, the connectors aretypically internal to the respective nodes and are not separatelydesignated, it being appreciated that alternatively discrete connectorsmay be employed.

It is appreciated that FIGS. 1A and 1B illustrates two embodiments of asystem providing electric power to plural LAN nodes via a hub andcommunication cabling connecting the hub to various LAN nodes. Anothertwo embodiments of a system providing electric power to plural LAN nodesvia a hub and communication cabling connecting the hub to various LANnodes are illustrated in FIGS. 2A & 2B. FIGS. 2A & 2B illustrate a localarea network including a power supply operative to provide electricalpower to local area network nodes over communication cabling.

In the illustrated embodiment of FIG. 2A, a conventional hub 100 doesnot provide electrical power over the communication cabling 101 and apower supply subsystem 130 is located externally of hub 100 and includesa power supply 132 which supplies operating power and/or backup power tovarious LAN nodes via the communication cabling 101. The communicationcabling connects a LAN switch 134 of conventional hub 100 to a combiner136 in power supply subsystem 130 and connects the combiner to thevarious LAN nodes. The combiner 136 provides electrical power from thepower supply 132 along the communication cabling to at least some of theLAN nodes. Bidirectional data communications from LAN switch 134 passthrough the combiner 136, substantially without interference.

Cabling 101 is preferably conventional LAN cabling having four pairs oftwisted copper wires cabled together under a common jacket. In theembodiment of FIG. 2A, as will be described hereinbelow, at least one ofthe pairs of twisted copper wires is employed for transmitting both dataand electrical power to nodes of the network. Typically two such pairsare employed for transmitting both data and electrical power along eachline connecting the power supply sub-system 130 to each node, while onesuch pair carries data only and a fourth pair is maintained as a spareand carries neither data nor power.

It is seen that the communication cabling 101 from the power supplysub-system 130 to the desktop computer 112, facsimile machine 116 andcomputer 120 carries both data and backup power, while the communicationcabling from the power supply sub-system 130 to the hub camera 114 andLAN telephone 118 carries both data and operating power and thecommunication cabling from the hub 100 to the server 122 carries onlydata and may, but need not pass through subsystem 130, in a typicallyLAN arrangement constructed and operative in accordance with a preferredembodiment of the present invention.

It is a particular feature of the embodiment of FIG. 2A that both dataand power are carried on the same twisted copper pair.

In the illustrated embodiment of FIG. 2A, each of the LAN nodes 112-120which receives power is provided with an external separator forseparating the data from the electrical power coupled to thecommunication cabling. The external separators associated withrespective nodes 112-120 are designated by respective reference numbers142-149. Each such separator has a communication cabling input andseparate data and power outputs. It is appreciated that some or all ofthe nodes 112-120 may alternatively be provided with internal separatorsand that some or all of the nodes 112-120 may be provided with externalseparators.

It is appreciated that in addition to the LAN nodes describedhereinabove, the present invention is useful with any other suitablenodes such as, for example, wireless LAN access points, emergencylighting system elements, paging loudspeakers, CCTV cameras, alarmsensors, door entry sensors, access control units, laptop computers,network elements such as hubs, switches and routers, monitors and memorybackup units for PCs and workstations.

In the illustrated embodiment of FIG. 2B, a conventional hub 150 doesnot provide electrical power over the communication cabling 151 and apower supply subsystem 180 is located externally of hub 150 and includesa power supply 182 which supplies operating power and/or backup power tovarious LAN nodes via the communication cabling 151. The communicationcabling connects a LAN switch 184 of conventional hub 150 to a powersupply interface 186 in power supply subsystem 180 and connects thepower supply interface 186 to the various LAN nodes. The power supplyinterface distributes electrical power from the power supply 182 alongthe communication cabling to at least some of the LAN nodes.Bidirectional data communications from LAN switch 184 pass through thepower supply interface 186, substantially without interference.

Cabling 151 is preferably conventional LAN cabling having four pairs oftwisted copper wires cabled together under a common jacket. In theembodiment of FIG. 2B, in contrast to the arrangement described abovewith respect to FIG. 2A and as will be described hereinbelow, at leastone of the pairs of twisted copper wires is employed only fortransmitting electrical power to nodes of the network and at least oneof the pairs of twisted copper wires is employed only for transmittingdata. Typically two such pairs are employed for transmitting data onlyand two such pairs are employed only for supplying electrical poweralong each line connecting a hub to each node.

It is seen that the communication cabling 151 from the hub 150 to thedesktop computer 162, facsimile machine 166 and computer 170 carriesboth data and backup power, while the communication cabling from the hub150 to the hub camera 164 and LAN telephone 168 carries both data andoperating power and the communication cabling from the hub 150 to theserver 172 carries only data and may, but need not pass throughsubsystem 180, in a typically LAN arrangement constructed and operativein accordance with a preferred embodiment of the present invention.

It is a particular feature of the embodiment of FIG. 2B that data andpower are carried on separate twisted copper pairs of each communicationcabling line.

In the illustrated embodiment of FIG. 2B, each of the LAN nodes 162-170which receives power is provided with an external connector forseparately providing data and electrical power from the communicationcabling. The external connector associated with respective nodes 162-170are designated by respective reference numbers 192-199. Each suchconnector has a communication cabling input and separate data and poweroutputs. It is appreciated that some or all of the nodes 162-170 mayalternatively be provided with internal connectors and that some or allof the nodes 162-170 may be provided with external connectors.

It is appreciated that in addition to the LAN nodes describedhereinabove, the present invention is useful with any other suitablenodes such as, for example, wireless LAN access points, emergencylighting system elements, paging loudspeakers, CCTV cameras, alarmsensors, door entry sensors, access control units, laptop computers,network elements, such as hubs, switches and routers, monitors andmemory backup units for PCs and workstations.

Reference is now made to FIG. 3A, which is a simplified block diagram ofa hub, such as hub 10, useful in the embodiment of FIG. 1A. Hub 10preferably comprises a conventional, commercially available, LAN switch34 which functions as a data communication switch/repeater and iscoupled to combiner 36. Combiner 36 typically comprises a plurality ofcouplers 220, each of which is connected via a filter 222 to a smartpower allocation and reporting circuit (SPEAR) 224. Each SPEAR 224 isconnected to power supply 32 for receiving electrical power therefrom.It is appreciated that power supply 32 may be physically locatedexternally of the hub 10. Power supply 32 may be provided with a powerfailure backup facility, such as a battery connection.

Each coupler 220 has two ports, one of which is preferably connected toa port of LAN switch 34 and the other of which is preferably connected,via communication cabling, to a LAN node.

Couplers 220 are preferably operative to couple electrical power to thecommunication cabling substantially without interfering with the datacommunication therealong.

Filters 222 are preferably operative to avoid unwanted interport andinterpair coupling, commonly known as “crosstalk” and to block noisefrom the power supply 32 from reaching the communication cabling.

A central management and control subsystem 226, typically embodied in amicrocontroller, preferably controls the operation of the power supply32, the LAN switch 34, the couplers 220, the filters 222 and the SPEARs224.

Reference is now made to FIG. 3B, which is a simplified block diagram ofa hub, such as hub 60, useful in the embodiment of FIG. 1B. Hub 60preferably comprises a conventional, commercially available, LAN switch84 which functions as a data communication switch/repeater and iscoupled to power supply interface 86. Power supply interface 86typically comprises a plurality of filters 272, each connected to asmart power allocation and reporting circuit (SPEAR) 274. Each SPEAR 274is connected to power supply 82 for receiving electrical powertherefrom. It is appreciated that power supply 82 may be physicallylocated externally of the hub 60. Power supply 82 may be provided with apower failure backup facility, such as a battery connection.

Filters 272 are preferably operative to avoid unwanted interportcoupling, commonly known as “crosstalk” and to block noise from thepower supply 82 from reaching the communication cabling.

A central management and control subsystem 276, typically embodied in amicrocontroller, preferably controls the operation of the power supply82, the LAN switch 84, the filters 272 and the SPEARs 274.

It is seen that in the embodiment of FIG. 3B, couplers are not providedinasmuch as power and data are transmitted over separate twisted pairs.The data carried on conductors via the power supply interface issubstantially unaffected by the operation of the power supply interface.

Reference is now made to FIG. 4A, which is a simplified block diagram ofhub 100 and the power supply subsystem 130 employed in the embodiment ofFIG. 2A. Hub 100 preferably comprises a conventional, commerciallyavailable, LAN switch 134 which functions as a data communicationswitch/repeater and is coupled to combiner 136 forming part of powersupply subsystem 130. Combiner 136 typically comprises a plurality ofcouplers 320, each of which is connected via a filter 322 to a smartpower allocation and reporting circuit (SPEAR) 324. Each SPEAR 324 isconnected to power supply 132 (FIG. 2A) for receiving electrical powertherefrom. It is appreciated that power supply 132 may be physicallylocated externally of the power supply subsystem 130. Power supply 132may be provided with a power failure backup facility, such as a batteryconnection.

Each coupler 320 has two ports, one of which is preferably connected toa port of LAN switch 134 and the other of which is preferably connected,via communication cabling, to a LAN node.

Couplers 320 are preferably operative to couple electrical power to thecommunication cabling substantially without interfering with the datacommunication therealong.

Filters 322 are preferably operative to avoid unwanted interport andinterpair coupling, commonly known as “crosstalk” and to block noisefrom the power supply 132 from reaching the communication cabling.

A central management and control subsystem 326, typically embodied in amicrocontroller, preferably controls the operation of the power supply132, the couplers 320, the filters 322 and the SPEARs 324.

Reference is now made to FIG. 4B, which is a simplified block diagram ofhub 150 and the power supply subsystem 180 employed in the embodiment ofFIG. 2B. Hub 150 preferably comprises a conventional, commerciallyavailable, LAN switch 184 which functions as a data communicationswitch/repeater and is coupled to power supply interface 186 formingpart of power supply subsystem 180. Power supply interface 186 typicallycomprises a plurality of filters 372 each coupled to a smart powerallocation and reporting circuit (SPEAR) 374. Each SPEAR 374 isconnected to power supply 182 (FIG. 2B) for receiving electrical powertherefrom. It is appreciated that power supply 182 may be physicallylocated externally of the power supply subsystem 180. Power supply 182may be provided with a power failure backup facility, such as a batteryconnection.

Filters 372 are preferably operative to avoid unwanted interport andinterpair coupling, commonly known as “crosstalk” and to block noisefrom the power supply 182 from reaching the communication cabling.

A central management and control subsystem 376, typically embodied in amicrocontroller, preferably controls the operation of the power supply182, filters 372 and the SPEARs 374.

It is seen that in the embodiment of FIG. 4B, couplers are not providedinasmuch as power and data are transmitted over separate twisted pairs.The data carried on conductors via the power supply interface issubstantially unaffected by the operation of the power supply interface.

It is appreciated that power supply 32 (FIG. 3A), power supply 82 (FIG.3B), power supply 132 (FIG. 4A) and power supply 182 (FIG. 4B) provideoutput power to SPEARs 224 (FIG. 3A), SPEARs 274 (FIG. 3B), 324 (FIG.4A) and 374 (FIG. 4B) respectively along a pair of conductors, one ofwhich is designated as a positive conductor and indicated by (+) and theother of which is designated as a negative conductor and indicated by(−). The voltages supplied to the respective positive and negativeconductors are designated respectively as+Vin and −Vin. The differencetherebetween is designated as Vin.

Reference is now made to FIG. 5, which is a simplified block diagramillustration of a smart power allocation and reporting circuit (SPEAR)400 useful in the embodiments of FIGS. 3A, 3B and FIGS. 4A, 4Bparticularly when DC current is coupled to the communication cabling.

SPEAR 400 preferably comprises a current sensor 402 which receives avoltage input +Vin from a power supply and generates a signal which isproportional to the current passing therethrough. A voltage input −Vinreceived from the power supply 32 (FIG. 3A), 82 (FIG. 3B), 132 (FIG. 4A)or 182 (FIG. 4B) provides a voltage output −Vout which is typicallyunchanged from voltage input −Vin.

The output of current sensor 402 is supplied to a multiplicity ofcomparators 404 which also receive respective reference voltages Vreffrom respective programmable reference voltage sources 406, typicallyimplemented in A/D converters. Programmable reference voltage sources406 receive control inputs from management & control circuits 226 (FIG.3A), 276 (FIG. 3B), 326 (FIG. 4A) and 376 (FIG. 4B) preferably via a bus407. Alternatively, voltage sources 406 need not be programmable.

The outputs of comparators 404 are supplied to a current limiter andswitch 408 which receives input voltage Vin via the current sensor 402and provides a current-limited voltage output Vout. Output voltages+Vout and −Vout are applied as inputs to an A/D converter 409 whichoutputs a digital indication of Vout, which is the difference between+Vout and −Vout, to the management & control circuits 226 (FIG. 3A), 276(FIG. 3B), 326 (FIG. 4A) and 376 (FIG. 4B) preferably via bus 407. Theoutputs of comparators 404 are supplied to management & control circuits226 (FIG. 3A), 276 (FIG. 3B), 326 (FIG. 4A) and 376 (FIG. 4B) preferablyvia bus 407 to serve as monitoring inputs providing informationregarding the DC current flowing through the SPEAR.

The outputs of some of comparators 404 are supplied directly to currentlimiter and switch 408, while the outputs of others of comparators 404are supplied thereto via a timer 410 and a flip/flop 412. Thecomparators whose outputs are supplied directly to current limiter andswitch 408 provide immediate current limiting at a relatively highthreshold, while the comparators whose outputs are supplied to currentlimiter and switch 408 via timer 410 and flip/flop 412 provide delayedaction current cut-off at a relatively low threshold.

Flip-flop 412 is responsive to external inputs which enable remotecontrol of the operation of the current limiter and switch 408 by themanagement & control circuits 226 (FIG. 3A), 276 (FIG. 3B), 326 (FIG.4A) and 376 (FIG. 4B) via bus 407.

It is appreciated that the above described SPEAR circuitry may also beoperated on the negative lead. In such a case a short-lead would beconnected between the Vin and the Vout.

It is further appreciated that the components of the SPEAR may also beorganize in an alternative sequence.

Reference is now made FIG. 6, which is a simplified schematicillustration of a preferred implementation of the embodiment of FIG. 5.Inasmuch as identical reference numerals are employed in both FIGS. 5and 6, the schematic illustration of FIG. 6 is believed to beself-explanatory and therefore, for the sake of conciseness, noadditional textual description thereof is provided herein.

Reference is now made to FIG. 7A, which is a simplified block diagramillustration of a LAN node interface circuit useful in the embodimentsof FIGS. 1A and 2A for example as external separators 142-149. It isappreciated that the circuitry of FIG. 7A alternatively may be built-into LAN nodes, as shown, for example in FIG. 1A.

FIG. 7A shows typical constituent elements of a network node 500,including a data transceiver 502, a mains-fed power supply 504 andvarious other elements 506 depending on the functionality of the node.The interface circuitry typically comprises a separator 508 which isoperative to receive data and electrical power over communicationcabling and to provide a data output to the data transceiver 502 and aseparate power output to a communications cabling-fed power supply 510,preferably forming part of network node 500, which preferably powers thedata transceiver 502 and possibly any other suitable circuitry.

Reference is now made to FIG. 7B, which is a simplified block diagramillustration of a LAN node interface circuit useful in the embodimentsof FIGS. 1B and 2B for example as external connectors 192-199. It isappreciated that the circuitry of FIG. 7B alternatively may be built-into LAN nodes, as shown, for example in FIG. 1B.

FIG. 7B shows typical constituent elements of a network node 550,including a data transceiver 552, a mains-fed power supply 554 andvarious other elements 556 depending on the functionality of the node.The interface circuitry typically comprises a connector 558 which isoperative to receive data and electrical power over communicationcabling and to provide a data output to the data transceiver 552 and aseparate power output to a communications cabling-fed power supply 560,preferably forming part of network node 550, which preferably powers thedata transceiver 552 and possibly any other suitable circuitry.

Reference is FIGS. 8A-8E, which are simplified block diagramillustrations of various embodiments of a coupler useful in theembodiments of FIGS. 3A and 4A. The various embodiments have the commonpurpose of coupling DC power to the communication cabling withoutupsetting the balance therealong, while producing a minimal change inthe line impedance thereof and preventing saturation or burnout of linetransformers coupled thereto.

FIG. 8A describes a coupler 600, such as coupler 220 (FIG. 3A) orcoupler 320 (FIG. 4A) suitable for use with a LAN in accordance with apreferred embodiment of the present invention and which includes a pairof additional transformers 610 for each channel. Transformers 610 aretypically 1:1 transformers which are characterized in that they includea center tap at the secondary via which the DC voltage is fed to bothwires of a twisted pair.

This structure maintains the balance of the line and prevents coresaturation. This structure also has the advantage that due to the factthat the same voltage is carried on both wires of the twisted pairsimultaneously, the occurrence of a short circuit therealong will notcause a power overload. An additional advantage of this structure isthat it will not cause burnout of a LAN node which is not speciallyadapted for receive power over the twisted pair.

FIG. 8B describes a coupler 620, such as coupler 220 (FIG. 3A) orcoupler 320 (FIG. 4A) suitable for use with a LAN in accordance with apreferred embodiment of the present invention and which includes a pairof additional transformers 630 for each channel. Transformers 630 aretypically 1:1 transformers which are characterized in that they includea secondary 632 which is split into two separate windings 634 and 636. Acapacitor 640 is connected between windings 634 and 636. The capacitoreffectively connects the two windings in series for high frequencysignals, such as data signals, but effectively isolates the two windingsfor DC.

This structure enables the two windings to carry respective positive andnegative voltages via the same twisted pair. An advantage of thisstructure is that it applies a net zero DC current via the twisted pairand thus eliminates the magnetic field that would otherwise have existedhad the twisted pair carried DC current in the same directions.

FIG. 8C describes a coupler 650, such as coupler 220 (FIG. 3A) orcoupler 320 (FIG. 4A) suitable for use with a LAN in accordance with apreferred embodiment of the present invention and which includes a pairof capacitors 660 which effectively block DC from reaching the LANswitch. This structure is relatively simple and does not require anadditional transformer.

FIG. 8D describes a coupler 670, such as coupler 220 (FIG. 3A) orcoupler 320 (FIG. 4A) suitable for use with a LAN in accordance with apreferred embodiment of the present invention and which includes twopairs of capacitors 680 and 690 which effectively block DC from reachingthe LAN switch. This structure is also relatively simple and does notrequire an additional transformer.

This structure also has the advantage that due to the fact that the samevoltage is carried on both wires of the twisted pair simultaneously, theoccurrence of a short circuit therealong will not cause a poweroverload. An additional advantage of this structure is that it will notcause burnout of a LAN node which is not specially adapted for receivepower over the twisted pair.

FIG. 8E describes a coupler 700, such as coupler 220 (FIG. 3A) orcoupler 320 (FIG. 4A) suitable for use with a LAN in accordance with apreferred embodiment of the present invention and which is aself-balancing common mode coupling circuit. Combiner 700 comprises twopairs of adjustable active balancing circuits 702 and 704, which areoperative in conjunction with respective sensing and control circuits706 and 708.

It is a particular feature of the embodiment of FIG. 8E that the twopairs of adjustable active balancing circuits 702 and 704, which areoperative in conjunction with respective sensing and control circuits706 and 708 are operative to maintain precisely identical voltages oneach of the two wires comprising a twisted pair coupled thereto.

Normally the output of a LAN switch is coupled to communication cablingvia an isolation transformer 710, which is not part of the coupler 700.When precisely identical voltages, as aforesaid, are applied to each ofthe two wires comprising the twisted pair, there is no DC voltage acrossthe secondary windings of the isolation transformer 710 and thus no DCcurrent flows therethrough. This obviates the need for DC isolatingcapacitors and thus improves the balancing and impedance matchingbehavior of the combiner.

It is appreciated that whereas in a theoretically ideal system therewould not be any need for active balancing as provided in the embodimentof FIG. 8E, in reality due to variations in the DC resistance along theentire communication cabling system, the DC voltages on each of the twowires of the twisted pair would not be identical in the absence ofactive balancing, thus creating a DC voltage drop across the secondaryof transformer 710 which could cause either saturation or burnout oftransformer 710.

Reference is now made FIG. 8F, which is a simplified schematicillustration of a preferred implementation of the embodiment of FIG. 8E.Inasmuch as identical reference numerals are employed in both FIGS. 8Eand 8F, the schematic illustration of FIG. 8F is believed to beself-explanatory and therefore, for the sake of conciseness, noadditional textual description thereof is provided herein.

Reference is now made FIG. 8G, which is a simplified schematicillustration of a preferred implementation of the embodiment of FIG. 8E.Inasmuch as identical reference numerals are employed in both FIGS. 8Eand 8G, the schematic illustration of FIG. 8G is believed to beself-explanatory and therefore, for the sake of conciseness, noadditional textual description thereof is provided herein.

Reference is now made to FIGS. 9A-9G which are simplified block diagramand schematic illustrations of various embodiments of a separator usefulin the embodiments of FIGS. 1A, 2A & 7A preferably in combination withthe respective combiners of FIGS. 8A-8G.

In addition to the components included in FIGS. 9A to 9G, theseseparators may also include appropriate filters to avoid interpair andinterport crosstalk.

The various embodiments have the common purpose of decoupling DC powerfrom the communication cabling without upsetting the balance therealong,while producing a minimal change in the line impedance thereof andpreventing saturation or burnout of line transformers coupled thereto.

FIG. 9A describes a separator 1600, such as separator 142 (FIG. 2A),suitable for use with a LAN in accordance with a preferred embodiment ofthe present invention and which includes a pair of additionaltransformers 1610 for each channel. Transformers 1610 are typically 1:1transformers which are characterized in that they include a center tapat the primary via which the DC voltage is extracted from both wires ofa twisted pair.

This structure maintains the balance of the line and prevents coresaturation. This structure also has the advantage that due to the factthat the same voltage is carried on both wires of the twisted pairsimultaneously, the occurrence of a short circuit therealong will notcause a power overload. An additional advantage of this structure isthat it will not cause burnout of a LAN node which is not speciallyadapted for receive power over the twisted pair.

FIG. 9B describes a separator 1620, such as separator 142 (FIG. 2A)suitable for use with a LAN in accordance with a preferred embodiment ofthe present invention and which includes a pair of additionaltransformers 1630 for each channel. Transformers 1630 are typically 1:1transformers which are characterized in that they include a primary 1632which is split into two separate windings 1634 and 1636. A capacitor1640 is connected between windings 1634 and 1636. The capacitoreffectively connects the two windings in series for high frequencysignals, such as data signals, but effectively isolates the two windingsfor DC.

This structure enables the two windings to carry respective positive andnegative voltages via the same twisted pair. An advantage of thisstructure is that it applies a net zero DC current via the twisted pairand thus eliminates the magnetic field that would otherwise have existedhad the twisted pair carried DC current in the same directions.

FIG. 9C describes a separator 1650, such as separator 142 (FIG. 2A),suitable for use with a LAN in accordance with a preferred embodiment ofthe present invention and which includes a pair of capacitors 1660 whicheffectively block DC from reaching the node circuits. This structure isrelatively simple and does not require an additional transformer.

FIG. 9D describes a separator 1670, such as separator 142 (FIG. 2A),suitable for use with a LAN in accordance with a preferred embodiment ofthe present invention and which includes two pairs of capacitors 1680and 1690 which effectively block DC from reaching the node circuits.This structure is also relatively simple and does not require anadditional transformer.

This structure also has the advantage that due to the fact that the samevoltage is carried on both wires of the twisted pair simultaneously, theoccurrence of a short circuit therealong will not cause a poweroverload. An additional advantage of this structure is that it will notcause burnout of a LAN node which is not specially adapted for receivepower over the twisted pair.

FIG. 9E describes a separator 1700, such as separator 142 (FIG. 2A),suitable for use with a LAN in accordance with a preferred embodiment ofthe present invention and which is a self-balancing common mode couplingcircuit. Separator 1700 comprises two pairs of adjustable activebalancing circuits 1702 and 1704, which are operative in conjunctionwith respective sensing and control circuits 1706 and 1708.

It is a particular feature of the embodiment of FIG. 9E that the twopairs of adjustable active balancing circuits 1702 and 1704, which areoperative in conjunction with respective sensing and control circuits1706 and 1708 are operative to maintain precisely identical voltages oneach of the two wires comprising a twisted pair coupled thereto.

Normally the input of a LAN node is coupled to communication cabling viaan isolation transformer 1710, which is not part of the separator 1700.When precisely identical voltages, as aforesaid, are maintained on eachof the two wires comprising the twisted pair, there is no DC voltageacross the primary windings of the isolation transformer 1710 and thusno DC current flows therethrough. This obviates the need for DCisolating capacitors and thus improves the balancing and impedancematching behavior of the separator.

It is appreciated that whereas in a theoretically ideal system therewould not be any need for active balancing as provided in the embodimentof FIG. 9E, in reality due to variations in the DC resistance along theentire communication cabling system, the DC voltages on each of the twowires of the twisted pair would not be identical in the absence ofactive balancing, thus creating a DC voltage drop across the primary oftransformer 1710 which could cause either saturation or burnout oftransformer 1710.

Reference is now made FIG. 9F, which is a simplified schematicillustration of part of a preferred implementation of the embodiment ofFIG. 9E, including elements 1702 and 1706 thereof. Inasmuch as identicalreference numerals are employed in both FIGS. 9E and 9F, the schematicillustration of FIG. 9F is believed to be self-explanatory andtherefore, for the sake of conciseness, no additional textualdescription thereof is provided herein.

Reference is now made FIG. 9G, which is a simplified schematicillustration of part of a preferred implementation of the embodiment ofFIG. 9E, including elements 1704 and 1708 thereof. Inasmuch as identicalreference numerals are employed in both FIGS. 9E and 9G, the schematicillustration of FIG. 9G is believed to be self-explanatory andtherefore, for the sake of conciseness, no additional textualdescription thereof is provided herein.

The circuits of FIGS. 9F and 9G is provided to ensure that the voltageis identical on both leads of the twisted pair to which they are coupledin order to prevent current flow through transformers 1710 (FIG. 9E).This is accomplished by the circuits of 9F and 9G by changing thecurrent flowing through the active filters 1702 and 1704 under thecontrol of elements 1706 and 1708 respectively.

Reference is now made to FIG. 10A, which is a simplified block diagramillustration of a communications network including power supply andmanagement over communications cabling constructed and operative inaccordance with a preferred embodiment of the present invention.

As seen in FIG. 10A, there is provided a local area network (LAN)comprising a hub 2010 which is coupled, by cabling, preferably astructured cabling system, to a plurality of LAN nodes, such as adesktop computer 2012, a web camera 2014, a facsimile machine 2016, aLAN telephone, also known as an IP telephone 2018, a computer 2020 and aserver 2022.

In accordance with a preferred embodiment of the present invention thereis provided a power supply subsystem 2030 which is operative to provideat least some operating or backup power to at least some of saidplurality of nodes via the hub 2010 and the communication cablingconnecting the hub to various LAN nodes.

In the illustrated embodiment of FIG. 10A, subsystem 2030 is locatedwithin the hub 2010 and includes a power supply 2032 which suppliesoperating power and/or backup power to various LAN nodes via thecommunication cabling. The communication cabling connects a LAN switch2034 via a combiner 2036 to the various LAN nodes. The combiner coupleselectrical power from the power supply 2032 along the communicationcabling to at least some of the LAN nodes. Bidirectional datacommunications from LAN switch 2034 pass through the combiner 2036,substantially without interference.

In accordance with a preferred embodiment of the present invention,there is provided in hub 2010 a power management & control unit 2038which monitors and controls the power supplied by subsystem 2030 to thevarious LAN nodes via the communications cabling. The power management &control unit 2038 preferably communicates with a management workstation2040, preferably via a LAN or a WAN. Management workstation 2040 isoperative, preferably under the control of an operator, to govern theoperation of power management & control unit 2038.

It is appreciated that a management workstation 2040 may govern theoperation of multiple power management & control units 2038. The powermanagement & control unit 2038 may also communicate with various LANnodes via LAN switch 2034 by providing standard LAN messages to thenodes thereby to govern their current mode of power usage. For example,power management & control unit 2038 may send control messages which aredecoded at the LAN nodes and are employed by controllers in thecircuitry of FIGS. 14A & 14B for controlling whether full or partialfunctionality is provided thereat.

In one specific case, when the power management & control unit 2038senses that mains power to power supply 2032 is not available, it maysend a control message via LAN switch 2034 to cause the various LANnodes to operate in a backup or reduced power mode.

It is seen that the communication cabling from the hub 2010 to thedesktop computer 2012, facsimile machine 2016 and computer 2020 carriesboth data and backup power, while the communication cabling from the hub2010 to the hub camera 2014 and LAN telephone 2018 carries both data andoperating power and the communication cabling from the hub to the server2022 carries only data, in a typically LAN arrangement constructed andoperative in accordance with a preferred embodiment of the presentinvention.

It is appreciated that each of the LAN nodes 2012-2020, which receivespower over the communication cabling, includes a separator forseparating the electrical power from the data. In the illustratedembodiment of FIG. 10A, the separators are typically internal to therespective nodes and are not separately designated, it being appreciatedthat alternatively discrete separators may be employed.

It is a particular feature of the embodiment of FIG. 10A that both dataand power are carried on the same twisted copper pair.

It is appreciated that FIG. 10A illustrates one embodiment of a systemproviding electric power to plural LAN nodes via a hub and communicationcabling connecting the hub to various LAN nodes. Another embodiment of asystem providing electric power to plural LAN nodes via a hub andcommunication cabling connecting the hub to various LAN nodes isillustrated in FIG. 11A. FIG. 11A illustrates a local area networkincluding a power supply and management unit operative to provideelectrical power to local area network nodes over communication cabling.

Reference is now made to FIG. 10B, which is a simplified block diagramillustration of a communications network including power supply andmanagement over communications cabling constructed and operative inaccordance with a preferred embodiment of the present invention.

As seen in FIG. 10B, there is provided a local area network (LAN)comprising a hub 2060 which is coupled, by cabling, preferably astructured cabling system, to a plurality of LAN nodes, such as adesktop computer 2062, a web camera 2064, a facsimile machine 2066, aLAN telephone, also known as an IP telephone 2068, a computer 2070 and aserver 2072.

In accordance with a preferred embodiment of the present invention thereis provided a power supply subsystem 2080 which is operative to provideat least some operating or backup power to at least some of saidplurality of nodes via the hub 2060 and the communication cablingconnecting the hub to various LAN nodes.

In the illustrated embodiment of FIG. 10B, subsystem 2080 is locatedwithin the hub 2060 and includes a power supply 2082 which suppliesoperating power and/or backup power to various LAN nodes via thecommunication cabling. The communication cabling connects a LAN switch2084 via a power supply interface 2086 to the various LAN nodes. Thepower supply interface provides electrical power from the power supply2082 along the communication cabling to at least some of the LAN nodes.Bidirectional data communications from LAN switch 2084 pass through thepower supply interface 2086, substantially without interference.

In accordance with a preferred embodiment of the present invention,there is provided in hub 2060 a power management & control unit 2088which monitors and controls the power supplied by subsystem 2080 to thevarious LAN nodes via the communications cabling. The power management &control unit 2088 preferably communicates with a management workstation2090, preferably via a LAN or a WAN. Management workstation 2090 isoperative, preferably under the control of an operator, to govern theoperation of power management & control unit 2088.

It is appreciated that a management workstation 2090 may govern theoperation of multiple power management & control units 2088. The powermanagement & control unit 2088 may also communicate with various LANnodes via LAN switch 2084 by providing standard LAN messages to thenodes thereby to govern their current mode of power usage. For example,power management & control unit 2088 may send control messages which aredecoded at the LAN nodes and are employed by controllers in thecircuitry of FIGS. 14A & 14B for controlling whether full or partialfunctionality is provided thereat.

In one specific case, when the power management & control unit 2088senses that mains power to power supply 2082 is not available, it maysend a control message via LAN switch 2084 to cause the various LANnodes to operate in a backup or reduced power mode.

It is seen that the communication cabling from the hub 2060 to thedesktop computer 2062, facsimile machine 2066 and computer 2070 carriesboth data and backup power, while the communication cabling from the hub2060 to the hub camera 2064 and LAN telephone 2068 carries both data andoperating power and the communication cabling from the hub to the server2072 carries only data, in a typically LAN arrangement constructed andoperative in accordance with a preferred embodiment of the presentinvention.

It is appreciated that each of the LAN nodes 2062-2070, which receivespower over the communication cabling, includes a connector forseparately providing electrical power and data. In the illustratedembodiment of FIG. 10B, the connectors are typically internal to therespective nodes and are not separately designated, it being appreciatedthat alternatively discrete connector may be employed.

It is a particular feature of the embodiment of FIG. 10B that data andpower are carried on separate twisted copper pairs of each communicationcabling line.

It is appreciated that FIG. 10B illustrates one embodiment of a systemproviding electric power to plural LAN nodes via a hub and communicationcabling connecting the hub to various LAN nodes. Another embodiment of asystem providing electric power to plural LAN nodes via a hub andcommunication cabling connecting the hub to various LAN nodes isillustrated in FIG. 11B. FIG. 11B illustrates a local area networkincluding a power supply and management unit operative to provideelectrical power to local area network nodes over communication cabling.

In the illustrated embodiment of FIG. 11A, a conventional hub 2100 doesnot provide electrical power over the communication cabling and a powersupply and management subsystem 2130 is located externally of hub 2100and includes a power supply 2132 which supplies operating power and/orbackup power to various LAN nodes via the communication cabling as wellas a power management & control unit 2133.

The communication cabling connects a LAN switch 2134 of conventional hub2100 to a combiner 2136 in power supply and management subsystem 2130and connects the combiner to the various LAN nodes. The combiner 2136couples electrical power from the power supply 2132 along thecommunication cabling to at least some of the LAN nodes. Bidirectionaldata communications from LAN switch 2134 pass through the combiner 2136,substantially without interference.

In accordance with a preferred embodiment of the present invention,there is provided in power supply and management subsystem 2130 powermanagement & control unit 2133 which monitors and controls the powersupplied by subsystem 2130 to the various LAN nodes via thecommunications cabling. The power management & control unit 2133preferably communicates with a management workstation 2140, preferablyvia a LAN or a WAN.

Management workstation 2140 is operative, preferably under the controlof an operator, to govern the operation of power management & controlunit 2133. It is appreciated that a management workstation 2140 maygovern the operation of multiple power management & control units 2133and may also govern the operation of multiple hubs 2100.

It is seen that the communication cabling from the hub 2100 to thedesktop computer 2112, facsimile machine 2116 and computer 2120 carriesboth data and backup power, while the communication cabling from the hub2100 to the hub camera 2114 and LAN telephone 2118 carries both data andoperating power and the communication cabling from the hub 2100 to theserver 2122 carries only data and may, but need not pass throughsubsystem 2130, in a typically LAN arrangement constructed and operativein accordance with a preferred embodiment of the present invention.

In the illustrated embodiment of FIG. 11A, each of the LAN nodes2112-2120 which receives power is provided with an external separatorfor separating the data from the electrical power coupled to thecommunication cabling. The external separators associated withrespective nodes 2112-2120 are designated by respective referencenumbers 2142-2150. Each such separator has a communication cabling inputand separate data and power outputs. It is appreciated that some or allof the nodes 2112-2120 may alternatively be provided with internalseparators and that some or all of the nodes 2112-2120 may be providedwith external separators.

It is appreciated that in addition to the LAN nodes describedhereinabove, the present invention is useful with any other suitablenodes such as, for example, wireless LAN access points, emergencylighting system elements, paging loudspeakers, CCTV cameras, alarmsensors, door entry sensors, access control units, laptop computers,network elements, such as hubs, switches and routers, monitors andmemory backup units for PCs and workstations.

In the illustrated embodiment of FIG. 1B, a conventional hub 2150 doesnot provide electrical power over the communication cabling and a powersupply and management subsystem 2180 is located externally of hub 2150and includes a power supply 2182 which supplies operating power and/orbackup power to various LAN nodes via the communication cabling as wellas a power management & control unit 2183.

The communication cabling connects a LAN switch 2184 of conventional hub2150 to a power supply interface 2186 in power supply and managementsubsystem 2180 and connects the combiner to the various LAN nodes. Thepower supply interface 2186 provides electrical power from the powersupply 2182 along the communication cabling to at least some of the LANnodes. Bidirectional data communications from LAN switch 2184 passthrough the power supply interface 2186, substantially withoutinterference.

In accordance with a preferred embodiment of the present invention,there is provided in power supply and management subsystem 2180 powermanagement & control unit 2183 which monitors and controls the powersupplied by subsystem 2180 to the various LAN nodes via thecommunications cabling. The power management & control unit 2183preferably communicates with a management workstation 2190, preferablyvia a LAN or a WAN.

Management workstation 2190 is operative, preferably under the controlof an operator, to govern the operation of power management & controlunit 2183. It is appreciated that a management workstation 2190 maygovern the operation of multiple power management & control units 2183and may also govern the operation of multiple hubs 2150.

It is seen that the communication cabling from the hub 2150 to thedesktop computer 2162, facsimile machine 2166 and computer 2170 carriesboth data and backup power, while the communication cabling from the hub2150 to the hub camera 2164 and LAN telephone 2168 carries both data andoperating power and the communication cabling from the hub 2150 to theserver 2172 carries only data and may, but need not pass throughsubsystem 2180, in a typically LAN arrangement constructed and operativein accordance with a preferred embodiment of the present invention.

In the illustrated embodiment of FIG. 11B, each of the LAN nodes2162-2170 which receives power is provided with an external connectorfor separately providing data and electrical power from thecommunication cabling. The external connectors associated withrespective nodes 2162-2170 are designated by respective referencenumbers 2192-2199. Each such connector has a communication cabling inputand separate data and power outputs. It is appreciated that some or allof the nodes 2162-2170 may alternatively be provided with internalconnectors and that some or all of the nodes 2162-2170 may be providedwith external connectors.

It is appreciated that in addition to the LAN nodes describedhereinabove, the present invention is useful with any other suitablenodes such as, for example, wireless LAN access points, emergencylighting system elements, paging loudspeakers, CCTV cameras, alarmsensors, door entry sensors, access control units, laptop computers,network elements, such as hubs, switches and routers, monitors andmemory backup units for PCs and workstations.

Reference is now made to FIG. 12A, which is a simplified block diagramillustration of a hub, such as hub 2010, useful in the embodiment ofFIG. 10A. Hub 2010 preferably comprises a conventional, commerciallyavailable, LAN switch, such as LAN switch 2034 (FIG. 10A), whichfunctions as a data communication switch/repeater and is coupled to acoupler and filter unit 2037 which includes couplers 220 and filters 222as shown in FIG. 3A and forms part of combiner 2036 (FIG. 10A).

The coupler and filter unit 2037 is connected to a plurality of smartpower allocation and reporting circuits (SPEARs) 2224. Each SPEAR 2224is connected to power supply 2032 (FIG. 10A) for receiving electricalpower therefrom. It is appreciated that power supply 2032 may bephysically located externally of the hub 2010. Power supply 2032 may beprovided with a power failure backup facility, such as a batteryconnection.

Power management & control unit 2038 (FIG. 10A), preferably includesSPEAR controllers 2160 which are preferably connected via a bus 2162 toa microprocessor 2164, a memory 2166 and communication circuitry 2168,which typically includes a modem. The power management & controlsubsystem 2038 is preferably operative to control the operation of allof the couplers, filters and SPEARs in combiner 2036 as well as tocontrol the operation of the power supply 2032. Power management &control subsystem 2038 preferably communicates with management workstation 2040 (FIG. 10A) in order to enable operator control andmonitoring of the power allocated to the various LAN nodes in variousoperational modes of the system.

Reference is now made to FIG. 12B, which is a simplified block diagramillustration of a hub, such as hub 2060, useful in the embodiment ofFIG. 10B. Hub 2060 preferably comprises a conventional, commerciallyavailable, LAN switch, such as LAN switch 2084 (FIG. 10B), whichfunctions as a data communication switch/repeater and is coupled to afilter unit 2087 which includes filters 222 as shown in FIG. 3B andforms part of power supply interface 2086 (FIG. 10B).

The filter unit 2087 is connected to a plurality of smart powerallocation and reporting circuits (SPEARs) 2274. Each SPEAR 2274 isconnected to power supply 2082 (FIG. 10B) for receiving electrical powertherefrom. It is appreciated that power supply 2082 may be physicallylocated externally of the hub 2060. Power supply 2082 may be providedwith a power failure backup facility, such as a battery connection.

Power management & control unit 2088 (FIG. 10B), preferably includesSPEAR controllers 2276 which are preferably connected via a bus 2278 toa microprocessor 2280, a memory 2282 and communication circuitry 2284,which typically includes a modem. The power management & controlsubsystem 2088 is preferably operative to control the operation of allof the filters and SPEARs in power supply interface 2086 as well as tocontrol the operation of the power supply 2082. Power management &control unit 2088 preferably communicates with management work station2090 (FIG. 10B) in order to enable operator control and monitoring ofthe power allocated to the various LAN nodes in various operationalmodes of the system.

Reference is now made to FIG. 13A, which is a simplified block diagramillustration of a hub and a power supply and management subsystem usefulin the embodiment of FIG. 11A. Hub 2100 (FIG. 11A) preferably comprisesa conventional, commercially available, LAN switch 2134 which functionsas a data communication switch/repeater and is coupled to combiner 2136forming part of power supply subsystem 2130.

Combiner 2136 includes a coupler and filter unit 2137 which includecouplers 320 and filters 322 as shown in FIG. 4A.

The coupler and filter unit 2137 is connected to a plurality of smartpower allocation and reporting circuits (SPEARs) 2324. Each SPEAR 2324is connected to power supply 2132 (FIG. 11A) for receiving electricalpower therefrom. It is appreciated that power supply 2132 may bephysically located externally of the power supply and managementsubsystem 2130. Power supply 2132 may be provided with a power failurebackup facility, such as a battery connection.

Power management & control unit 2133 (FIG. 11A), preferably includesSPEAR controllers 2360 which are preferably connected via a bus 2362 toa microprocessor 2364, a memory 2366 and communication circuitry 2368,which typically includes a modem. The power management & control unit2133 is preferably operative to control the operation of all of thecouplers, filters and SPEARs in combiner 2136 as well as to control theoperation of the power supply 2132.

Power management & control subsystem 2133 preferably communicates withmanagement work station 2140 (FIG. 11A) in order to enable operatorcontrol and monitoring of the power allocated to the various LAN nodesin various operational modes of the system.

Reference is now made to FIG. 13B, which is a simplified block diagramillustration of a hub and a power supply and management subsystem usefulin the embodiment of FIG. 11B. Hub 2150 (FIG. 11B) preferably comprisesa conventional, commercially available, LAN switch 2184 which functionsas a data communication switch/repeater and is coupled to power supplyinterface 2186 forming part of power supply subsystem 2180.

Power supply interface 2186 includes a filter unit 2187 which includesfilters 372 as shown in FIG. 4B.

The filter unit 2187 is connected to a plurality of smart powerallocation and reporting circuits (SPEARs) 2374. Each SPEAR 2374 isconnected to power supply 2182 (FIG. 11B) for receiving electrical powertherefrom. It is appreciated that power supply 2182 may be physicallylocated externally of the power supply and management subsystem 2180.Power supply 2182 may be provided with a power failure backup facility,such as a battery connection.

Power management & control unit 2183 (FIG. 11B), preferably includesSPEAR controllers 2376 which are preferably connected via a bus 2378 toa microprocessor 2380, a memory 2382 and communication circuitry 2384,which typically includes a modem. The power management & control unit2183 is preferably operative to control the operation of all of thefilters and SPEARs in power supply interface 2186 as well as to controlthe operation of the power supply 2182.

Power management & control unit 2183 preferably communicates withmanagement work station 2190 (FIG. 11B) in order to enable operatorcontrol and monitoring of the power allocated to the various LAN nodesin various operational modes of the system.

Reference is now made to FIGS. 14A & 14B, which are simplified blockdiagrams of two different node configurations useful in the embodimentsof FIGS. 10A, 10B, A and 11B.

The circuitry seen in FIG. 14A includes circuitry which is preferablyembodied in a node, parts of which circuitry may alternatively beembodied in a separator or connector associated with that node.

The node, whatever its nature, for example any of nodes 2012-2020 inFIG. 10A, 2062-2070 in FIG. 101B, 2112-2120 in FIG. 11A or 2162-2170 inFIG. 11B, typically includes circuitry which is required for both fullfunctionality and reduced functionality operation, here termed“essential circuitry” and designated by reference numeral 2400, andcircuitry which is not required for reduced functionality operation,here termed “non-essential circuitry” and designated by referencenumeral 2402. For example, if the node comprises an IP telephone, theessential circuitry 2400 includes that circuitry enabling a user tospeak and hear over the telephone, while the non-essential circuitry2402 provides ancillary functions, such as automatic redial, telephonedirectory and speakerphone functionality.

The circuitry 2400 and 2402 which is typically part of the node isindicated by reference numeral 2404. Other circuitry, which may or maynot be incorporated within the node will now be described. A powersupply 2406, such as power supply 510 (FIG. 7A) or 560 (FIG. 7B)receives electrical power via communication cabling from a separator,such as separator 508 shown in FIG. 7A or from a connector, such asconnector 558 shown in FIG. 7B. The power supply 2406 supplieselectrical power separately to the essential circuitry 2400 and via aswitch 2410 to the non-essential circuitry 2402. Switch 2410 may alsoreceive and control the transfer of electrical power from a power supply2412 which is connected to mains power.

Switch 2410 receives a control input from a controller 2414 which istypically a conventional microcontroller providing a binary output.Controller 2414 receives a control input from a sensor 2416. Preferablycontroller 2414 also receives a control input from power supply 2412.

Sensor 2416 may be implemented in a number of possible ways. It may, forexample, sense the voltage level of the electrical power being suppliedto power supply 2406. Additionally or alternatively, it may sense acontrol signal transmitted thereto, such as a signal transmitted via thecommunication cabling from the power management & control unit 2038 viathe combiner 2036 (FIG. 10A) or from similar circuitry in the embodimentof FIG. 11A. Alternatively, it may sense a control signal transmittedthereto, such as a signal transmitted via the communication cabling fromthe power management & control unit 2088 via the power supply interface2086 (FIG. 10B) or from similar circuitry in the embodiment of FIG. 11B.

The sensor 2416 may receive inputs from either or both the power anddata outputs of separator 508 (FIG. 7A) or connector 558 (FIG. 7B). Theinput that it receives from the data output of separator 508 orconnector 558 may be tapped from an input to the essential circuitrywhich may include control signal decoding functionality, but preferablymay be derived from an output of the essential circuitry which providesa decoded control signal.

The functionality of controller 2414 may be summarized as follows: Whenthe controller 2414 receives a control input from power supply 2412indicating that mains power is available, it operates switch 2410 suchthat power is supplied to both essential circuitry 2400 andnon-essential circuitry 2402.

When mains power is not available via power supply 2412, but sensor 2416indicates that sufficient power is available via the communicationscabling, controller 2414 operates switch 2410 such that power issupplied to both essential circuitry 2400 and non-essential circuitry2402.

When, however, mains power is not available via power supply 2412 andsensor 2416 indicates that sufficient power is not available, controlleroperates switch 2410 such that adequate power is supplied with highestpriority to the essential circuitry 2400. If additional power beyondthat required by essential circuitry 2400 is also available, it may besupplied to the non-essential circuitry 2402 via switch 2410.

Alternatively, the operation of switch 2410 by the controller 2414 maynot be determined solely or at all by the power available, but rathersolely by control signals sensed by sensor 2416, wholly or partiallyindependently of the available power.

Reference is now made to FIG. 14B. The circuitry seen in FIG. 14Bincludes circuitry which is preferably embodied in a node, parts ofwhich circuitry may alternatively be embodied in a separator orconnector associated with that node. A power supply 2436, such as powersupply 510 (FIG. 7A) or 560 (FIG. 7B) receives electrical power viacommunication cabling from a separator, such as separator 508 shown inFIG. 7A or from a connector, such as connector 558 shown in FIG. 7B. Thepower supply 2436 supplies electrical power via a switch 2438 to thecircuitry 2440 of the node. Switch 2438 may also receive electricalpower from a power supply 2442 which is connected to mains power.

Switch 2438 receives a control input from a controller 2444 which istypically a conventional microcontroller providing a binary output.Controller 2444 receives a control input from a sensor 2446 as well as acontrol input from monitoring circuitry 2448. Monitoring circuitry 2448,which is continually powered by power supply 2436 or power supply 2442,senses a need of the LAN node to shift to full-functionality from sleepmode functionality. It may sense this need, for example, by receiving auser input indicating an intention to use the node or by receiving acontrol message via the communications cabling. Controller 2444 may alsoreceive a control input from power supply 2442.

Sensor 2446 may be implemented in a number of possible ways. It may, forexample, sense the voltage level of the electrical power being suppliedto power supply 2446. Additionally or alternatively, it may sense acontrol signal transmitted thereto, such as a signal transmitted via thecommunication cabling from the power management & control unit 2038 viathe combiner 2036 (FIG. 10A) or from similar circuitry in the embodimentof FIG. 11A. Alternatively, it may sense a control signal transmittedthereto, such as a signal transmitted via the communication cabling fromthe power management & control unit 2088 via the power supply interface2086 (FIG. 110B) or from similar circuitry in the embodiment of FIG.11B.

The functionality of controller 2444 may be summarized as follows: Inthe absence of an indication to the contrary from the monitoringcircuitry 2448 or from sensor 2446, the controller operates switch 2438so that circuitry 2440 does not operate. When a suitable input isreceived either from the monitoring circuitry 2448 or from sensor 2446,indicating a need for operation of circuitry 2440, the controller 2444operates switch 2438 to cause operation of circuitry 2444.

Reference is now made to FIG. 15. The circuitry seen in FIG. 15 includescircuitry which is preferably embodied in a node, parts of whichcircuitry may alternatively be embodied in a separator associated withthat node.

The node, whatever its nature, for example any of nodes 2012-2020 inFIG. 10A, 2062-2070 in FIG. 10B, 2112-2120 in FIG. 11A or 2162-2170 inFIG. 11B, typically includes circuitry which is required for both fullfunctionality and reduced functionality operation, here termed“essential circuitry” and designated by reference numeral 2500, andcircuitry which is not required for reduced functionality operation,here termed “non-essential circuitry” and designated by referencenumeral 2502. For example, if the node comprises an IP telephone, theessential circuitry 2500 includes that circuitry enabling a user tospeak and hear over the telephone, while the non-essential circuitry2502 provides ancillary functions, such as automatic redial, telephonedirectory and speakerphone functionality.

The circuitry 2500 and 2502 which is typically part of the node isindicated by reference numeral 2504. Other circuitry, which may or maynot be incorporated within the node will now be described.

A power supply 2506, such as power supply 510 (FIG. 7A) or 560 (FIG. 7B)receives electrical power via communication cabling from a separator,such as separator 508 shown in FIG. 7A or connector 558 shown in FIG.7B. The power supply 2506 supplies electrical power separately via aswitch 2508 to the essential circuitry 2500 and via a switch 2510 to thenon-essential circuitry 2502. Switches 2508 and 2510 may also receiveand control the transfer of electrical power from a power supply 2512which is connected to mains power.

Switches 2508 and 2510 each receive a control input from a controller2514 which is typically a conventional microcontroller providing abinary output. Controller 2514 receives a control input from a sensor2516. Preferably controller 2514 also receives a control input frompower supply 2512.

Sensor 2516 may be implemented in a number of possible ways. It may, forexample, sense the voltage level of the electrical power being suppliedto power supply 2506. Additionally or alternatively, it may sense acontrol signal transmitted thereto, such as a signal transmitted via thecommunication cabling from the power management & control unit 2038 viathe combiner 2036 (FIG. 10A) or from similar circuitry in the embodimentof FIG. 11A. Alternatively, it may sense a control signal transmittedthereto, such as a signal transmitted via the communication cabling fromthe power management & control unit 2088 via the power supply interface2086 (FIG. 10B) or from similar circuitry in the embodiment of FIG.111B.

The sensor 2516 may receive inputs from either or both the power anddata outputs of separator 508 (FIG. 7A) or connector 558 (FIG. 7B). Theinput that it receives from the data output of separator 508 or fromconnector 558 may be tapped from an input to the essential circuitrywhich may include control signal decoding functionality, but preferablymay be derived from an output of the essential circuitry which providesa decoded control signal.

Monitoring circuitry 2540, which is continually powered by power supply2506 or power supply 2512, senses a need of the LAN node to shift tofull-functionality from sleep mode functionality. It may sense thisneed, for example, by receiving a user input indicating an intention touse the node or by receiving a control message via the communicationscabling.

The functionality of controller 2514 may be summarized as follows: Whenthe controller 2514 receives a control input from power supply 2512indicating that mains power is available, it operates switches 2508 and2510 such that power is supplied to both essential circuitry 2500 andnon-essential circuitry 2502.

When mains power is not available via power supply 2512, but sensor 2516indicates that sufficient power is available via the communicationscabling, controller 2514 operates switches 2508 and 2510 such that poweris supplied to both essential circuitry 2500 and non-essential circuitry2502.

When, however, mains power is not available via power supply 2512 andsensor 2516 indicates that sufficient power is not available, controlleroperates switch 2508 such that adequate power is supplied with highestpriority to the essential circuitry 2500. If additional power beyondthat required by essential circuitry 2500 is also available, it may besupplied to the non-essential circuitry 2502 via switch 2510.

Alternatively, the operation of switch 2510 by the controller 2514 maynot be determined solely or at all by the power available, but rathersolely by control signals sensed by sensor 2516, wholly or partiallyindependently of the available power.

In the absence of an indication to the contrary from the monitoringcircuitry 2540 or from sensor 2516, the controller operates switch 2508so that circuitry 2500 does not operate. When a suitable input isreceived either from the monitoring circuitry 2540 or from sensor 2516,indicating a need for operation of circuitry 2500, the controller 2514operates switch 2508 to cause operation of circuitry 2500.

In accordance with a preferred embodiment of the present invention, thepower supply 2406 in the embodiment of FIG. 14A, 2436 in the embodimentof FIGS. 14B and 2506 in the embodiment of FIG. 15 may be constructed toinclude rechargeable energy storage elements. In such an arrangement,these power supplies provide limited back-up power for use in the caseof a power failure or any other suitable circumstance. They may alsoenable intermittent operation of LAN nodes in situations where only verylimited power may be transmitted over the communication cabling.

Reference is now made to FIG. 16, which is a generalized flowchartillustrating power management in both normal operation and reduced powermodes of the networks of FIGS. 10A, 10B, 11A and 11B. As seen in FIG.16, the power management & control unit 2038 (FIG. 10A), 2088 (FIG.10B), 2133 (FIG. 11A) or 2138 (FIG. 11B) governs the supply of power toat least some LAN nodes via the communications cabling, preferably inaccordance with a predetermined functionality which is describedhereinbelow with reference to FIG. 17.

The power management & control unit 2038 (FIG. 10A), 2088 (FIG. 10B),2133 (FIG. 11A) or 2138 (FIG. 11B) monitors and manages the powerconsumption of those LAN nodes. It senses overcurrent situations andeffects power cutoffs as appropriate. The power management & controlunit 2038 (FIG. 10A), 2088 (FIG. 10B), 2133 (FIG. 11A) or 2138 (FIG.11B) may operate in either an involuntary power management mode or avoluntary power management mode. Normally the mode of operation isselected at the time that the LAN is configured, however, it is possiblefor mode selection to take place thereafter.

In an involuntary power management mode of operation, if the powermanagement & control unit senses a situation of insufficient poweravailability for power transmission over the communications cabling tothe LAN nodes, it supplies a reduced amount of power to at least some ofthe LAN nodes and may also provide control messages or other controlinputs to the LAN nodes to cause them to operate in a reduced powermode. In a voluntary power management mode of operation, reduced poweravailability is mandated by management at certain times of reducedactivity, such as nights and weekends, in order to save energy costs

Reference is now made to FIG. 17, which illustrates a preferredmethodology for supply of electrical power to at least some of the LANnodes in accordance with the present invention.

Following initialization of hub 2010 (FIG. 10A), 20260 (FIG. 10B) orpower supply and management subsystem 2130 (FIG. 11A), 2180 (FIG. 1B)the communications cabling connection to nodes, to which it is intendedto transmit power over the communications cabling, is interrogated.

Initialization of hub 2010 (FIG. 10A), 20260 (FIG. 10B) or subsystem2130 (FIG. 11A), 2180 (FIG. 11B) preferably includes automaticallyactuated test procedures which ensure proper operation of the elementsof the hub 2010 (FIG. 10A), 20260 (FIG. 10B) or subsystem 2130 (FIG.11A), 2180 (FIG. 1B) communication with management work station 2040(FIG. 10A), 2090 (FIG. 10B), 2140 (FIG. 11A) or 2190 (FIG. 1B) ifpresent to determine desired operational parameters of the hub for eachnode and setting up an internal data base including desired operationalparameters for each node. During normal operation of the system, thevarious operational parameters for each node may be modified by anoperator employing the management work station 2040 (FIG. 10A), 2090(FIG. 10B), 2140 (FIG. 11A), 2190 (FIG. 11B).

The interrogation is described hereinbelow in greater detail withreference to FIGS. 18A and 18B.

If the node being interrogated is determined to have power-over-LAN typecharacteristics and is classified in the internal data base as a node towhich it is intended to transmit power over the communications cabling,the SPEAR parameters are set based on the contents of the internal database and power is transmitted to the node via the communicationscabling. Where appropriate, suitable signaling messages are sent to theremote node and the status of the line connected to the node is reportedto the management work station 2040.

The foregoing procedure is then repeated sequentially for each line ofthe hub 2110 or subsystem 2130, to which it is intended to transmitpower over the communications cabling.

Reference is now made to FIGS. 18A and 18B, which together are aflowchart illustrating a preferred embodiment of the interrogation andinitial power supply functionality which appears in FIG. 17.

As seen in FIGS. 18A & 18B, initially the voltage is measured at theoutput of the SPEAR 224 (FIG. 3A), 274 (FIG. 3B), 324 (FIG. 4A) or 374(FIG. 4B) corresponding to a line to which it is intended to transmitpower over the communications cabling. If the absolute value of thevoltage is higher than a predetermined programmable threshold V1, theline is classified as having a voltage present thereon from an externalsource. In such a case power is not supplied thereto over thecommunications cabling.

If the absolute value of the voltage is not higher than thepredetermined programmable threshold V1, the SPEAR current limit 10 isset to a predetermined programmable value IL1. SPEAR switch 408 (FIG. 5)is turned ON.

The voltage and the current at the output of the SPEAR are measured,typically at three predetermined programmable times T1, T2 and T3. TimesT1, T2 and T3 are typically determined by a time constant determined bythe inductance of typical NIC transformers and the maximum roundtrip DCresistance of a maximum allowed length of communications cabling betweenthe hub and a node. Typically, T1, T2 and T3 are equal to 1, 2 and 10times the above time constant.

Typical values for T1, T2 and T3 are 4 msec, 8 msec and 40 msec,respectively.

Based on these measurements the status of the node and the line to whichit is connected are determined. A typical set of determinations is setforth hereinbelow: NO LOAD   WHEN Vout > V2 AND THE ABSOLUTE VALUE OF 10< I2 FOR ALL T1, T2, T3 SHORT CIRCUIT WHEN Vout < V3 AND THE ABSOLUTEVALUE OF IO FOR ALL T1, T2, T3 NIC LOAD   WHEN VoutT3 < V4 AND THEABSOLUTE VALUE OF IOT1<IOT2<IOT3 POL LOAD   WHEN Vout T1>V5 ANDVoutT2>V5 AND VoutT3>V5 AND THE ABSOLUTE VALUE OF IOT1>I5 OR THEABSOLUTE VALUE OF IOT2>I5 OR THE ABSOLUTE VALUE OF IOT3>I5. WHERE

A NO LOAD condition is one in which a node is not connected to the line.

A SHORT CIRCUIT condition is one in which a short circuit exists acrossthe positive and negative conductors of the line upstream of the node orin the node.

A NIC LOAD condition is one in which a Network Interface Card linetransformer is connected across the line at the node.

A POL LOAD condition is one in which a Power Over LAN separator isconnected across the line at the node.

V0 is the voltage at the output of the SPEAR.

V1 is a predetermined programmable value which is preferably arrived atby measuring the highest peak value of voltage Vout for a period of afew minutes when switch 408 is OFF. This value is typically multipliedby 2 to arrive at V1. V1 is typically equal to 3 Volts.

V2 is a predetermined programmable value which is preferably arrived atby measuring the lowest value of voltage Vout for a period of a fewminutes when switch 408 is ON and when no load is connected between+Vout and −Vout at the output of each coupler 220 (FIG. 3A) and 320(FIG. 4A). A typical value of V2 is 80% of Vin.

V3 is a predetermined programmable value which is preferably arrived atby measuring the highest peak value of voltage Vout for a period of afew minutes when switch 408 is ON and when a resistance, whichcorresponds to the maximum roundtrip DC resistance of a maximum allowedlength of communications cabling between the hub and a node, typically50 ohms, is connected between +Vout and −Vout at the output of eachcoupler 220 (FIG. 3A) and 320 (FIG. 4A). This value is typicallymultiplied by 2 to arrive at V1. V1 is typically equal to 3 Volts.

V4 is a predetermined programmable value which is preferably arrived atby measuring the highest peak value of voltage Vout for a period of afew minutes when switch 408 is ON and when a resistance, whichcorresponds to the maximum roundtrip DC resistance of a maximum allowedlength of communications cabling between the hub and a node and theresistance of a NIC transformer, typically totaling 55 ohms, isconnected between +Vout and −Vout at the output of each coupler 220(FIG. 3A) and 320 (FIG. 4A). This value is typically multiplied by 2 toarrive at V1. V1 is typically equal to 3 Volts.

V5 is a predetermined programmable value which is preferably 50% of Vin,which represents a typical threshold value of Vin at which power supply510 (FIG. 7) commence operation.

-   -   VoutT1 is Vout measured at time T1;    -   VoutT2 is Vout measured at time T2;    -   VoutT3 is Vout measured at time T3;    -   IO is the current flowing +Vout to −Vout which is measured by        sensor 402 (FIG. 5)

IL1 is the predetermined programmable value of the current limit ofswitch 408 (FIG. 5) and is determined by the maximum allowable DCcurrent through the NIC transformer which does not result in saturationor burnout thereof. IL1 is typically in the vicinity of 10 mA.

12 is a predetermined programmable value which is preferably arrived atby measuring the maximum peak value of the current 10 for a period of afew minutes when switch 408 is ON and when no load is connected between+Vout and −Vout at the output of each coupler 220 (FIG. 3A) and 320(FIG. 4A). A typical value of 12 is 1 mA.

13 is a predetermined programmable value which is preferably arrived atby measuring the minimum value of the current 10 for a period of a fewminutes when switch 408 is ON and when a resistance, which correspondsto the maximum roundtrip DC resistance of a maximum allowed length ofcommunications cabling between the hub and a node, typically 50 ohms, isconnected between +Vout and −Vout at the output of each coupler 220(FIG. 3A) and 320 (FIG. 4A). 13 is typically equal to 80% of IL1.

I5 is a predetermined programmable value which is preferably arrived atby measuring the maximum peak value of the current 10 for a period of afew minutes when switch 408 is ON and when no load is connected between+Vout and −Vout at the output of each coupler 220 (FIG. 3A) and 320(FIG. 4A). This maximum peak value is multiplied by a factor, typically2. A typical value of 15 is 2 mA.

-   -   IOT1 is IO measured at time T1;    -   IOT2 is IO measured at time T2;    -   IOT3 is IO measured at time T3;

Reference is now made to FIGS. 19A-19D, 20A-20D, 21A-21D, 22A-22D,23A-23D and 24A-24D, which illustrate various functionalities formonitoring and managing power consumption in accordance with a preferredembodiment of the present invention. Most or all of the functionalitiesdescribed hereinbelow employ a basic monitoring and managing techniquewhich is now described:

In accordance with a preferred embodiment of the present invention, thefunctionality for monitoring and managing power consumption duringnormal operation includes sensing current on all lines. This ispreferably carried out in a generally cyclic manner. The sensed currentis compared with programmably predetermined reference values for eachline. Alternatively or additionally, voltage may be sensed and employedfor this purpose. On the basis of this comparison, each node isclassified as being over-current, under-current or normal. Theover-current classification may have programmably adjustable thresholds,such as high over-current, and regular over-current. The normalclassification may have sub-classifications, such as active mode, sleepmode, and low-power mode.

The system is operative to control the operation of nodes classified asbeing over-current in the following manner: If the current at a nodeexceeds a regular over current threshold for at least a predeterminedtime, power to that node is cut off after the predetermined time. In anyevent, current supplied to a node is not permitted to exceed the highover-current threshold. In accordance with a preferred embodiment of thepresent invention, various intermediate thresholds may be definedbetween the regular over-current threshold and the high over-currentthreshold and the aforesaid predetermined time to cut-off is determinedas a function of which of such intermediate thresholds is exceeded.

The system is operative to control the operation of nodes classified asbeing under-current in the following manner: Within a relatively shortpredetermined time following detection of an under-current node, whichpredetermined time is selected to avoid undesired response to noise,supply of current to such node is terminated.

In parallel to the functionality described hereinabove, the overallcurrent flow to all of the nodes over all of the lines is monitored.This monitoring may take place in a centralized manner or alternativelymay be based on an extrapolation of information received in theline-by-line monitoring described hereinabove.

The sensed overall current is compared with a programmably predeterminedreference value. On the basis of this comparison, the entire hub and thenodes connected thereto are together classified as being over-current ornormal. The over-current classification may have programmably adjustablethresholds, such as high over-current, and regular over-current.

The system is operative to control the operation of hubs classified asbeing over-current in the following manner: If the overall currentexceeds a regular overall over-current threshold for at least apredetermined time, power to at least some nodes is either reduced orcut off after the predetermined time. In any event, the overall currentis not permitted to exceed the high overall over-current threshold. Inaccordance with a preferred embodiment of the present invention, variousintermediate thresholds may be defined between the regular overallover-current threshold and the high overall over-current threshold andthe aforesaid predetermined time to cut-off is determined as a functionof which of such intermediate thresholds is exceeded.

Additionally in parallel to the functionality described hereinabove, thesystem is operative to report either continuously or intermittently, thecurrent level classification of each node and of the entire hub to anexternal monitoring system.

Further in parallel to the functionality described hereinabove, thesystem is operative to notify nodes of the impending change in thecurrent supply thereto.

Reference is now made to FIGS. 19A, 19B, 19C and 19D, which aregeneralized flowcharts each illustrating one possible mechanism for fullor no functionality operation in an involuntary power management step inthe flowchart of FIG. 16.

FIG. 19A illustrates a basic technique useful for full or nofunctionality operation in involuntary power management in accordancewith a preferred embodiment of the present invention. As seen in FIG.19A, the system initially determines the total power available to it aswell as the total power that it is currently supplying to all nodes. Therelationship between the current total power consumption (TPC) to thecurrent total power availability (TPA) is then determined.

If TPC/TPA is less than typically 0.8, additional nodes are suppliedfull power one-by-one on a prioritized basis. If TPC/TPA is greater thantypically 0.95, power to individual nodes is disconnected one-by-one ona prioritized basis.

If TPC/TPA is equal to or greater than typically 0.8 but less than orequal to typically 0.95, an inquiry is made as to whether a new noderequires power. If so, and a node having a lower priority is currentlyreceiving power, the lower priority node is disconnected from power andthe higher priority node is connected to power.

FIG. 19B illustrates a technique useful for full or no functionalityoperation with emergency override in involuntary power management inaccordance with a preferred embodiment of the present invention. Thetechnique of FIG. 19B can be used in the environment of thefunctionality of FIG. 19A.

As seen in FIG. 19B, the system senses an emergency need for power at agiven node. In such a case, the given node is assigned the highestpriority and the functionality of FIG. 19A is applied. Once theemergency situation no longer exists, the priority of the given node isreturned to its usual priority and the functionality of FIG. 19Aoperates accordingly.

FIG. 19C illustrates a technique useful for full or no functionalityoperation having queue-controlled priority in involuntary powermanagement in accordance with a preferred embodiment of the presentinvention. As seen in FIG. 19C, the system initially determines thetotal power available to it as well as the total power that it iscurrently supplying to all nodes. The relationship between the currenttotal power consumption (TPC) to the current total power availability(TPA) is then determined.

If TPC/TPA is less than typically 0.8, additional nodes are suppliedfull power one-by-one on a queue-controlled, prioritized basis,typically on a first come, first served basis. If TPC/TPA is greaterthan typically 0.95, power to individual nodes is disconnectedone-by-one on a prioritized basis.

If TPC/TPA is equal to or greater than typically 0.8 but less than orequal to typically 0.95, an inquiry is made as to whether a new noderequires power. If so, that node is added to the bottom of the queue.

FIG. 19D illustrates a technique useful for full or no functionalityoperation having queue-controlled priority in involuntary powermanagement in accordance with a preferred embodiment of the presentinvention. As seen in FIG. 19D, the system initially determines thetotal power available to it as well as the total power that it iscurrently supplying to all nodes. The relationship between the currenttotal power consumption (TPC) to the current total power availability(TPA) is then determined.

If TPC/TPA is less than typically 0.8, additional nodes are suppliedfull power one-by-one on a time-sharing, prioritized basis, typically ona basis that the node having the longest duration of use is cut offfirst. If TPC/TPA is greater than typically 0.95, power to individualnodes is disconnected one-by-one on a prioritized basis.

If TPC/TPA is equal to or greater than typically 0.8 but less than orequal to typically 0.95, an inquiry is made as to whether a new noderequires power. If so, and a node having a lower priority, in the sensethat it has been receiving power for a longer time, which is above apredetermined minimum time, is currently receiving power, the lowerpriority node is disconnected from power and the higher priority node isconnected to power.

It is appreciated that normally it is desirable that the node beinformed in advance in a change in the power to be supplied thereto.This may be accomplished by signally along the communications cabling ina usual data transmission mode or in any other suitable mode.

Reference is now made to FIGS. 20A, 20B, 20C and 20D, which aregeneralized flowcharts each illustrating one possible mechanism for fullor reduced functionality operation in an involuntary power managementstep in the flowchart of FIG. 16.

FIG. 20A illustrates a basic technique useful for full or reducedfunctionality operation in involuntary power management in accordancewith a preferred embodiment of the present invention. As seen in FIG.20A, the system initially determines the total power available to it aswell as the total power that it is currently supplying to all nodes. Therelationship between the current total power consumption (TPC) to thecurrent total power availability (TPA) is then determined.

If TPC/TPA is less than typically 0.8, additional nodes are suppliedfull power one-by-one on a prioritized basis. If TPC/TPA is greater thantypically 0.95, power to individual nodes is reduced one-by-one on aprioritized basis.

If TPC/TPA is equal to or greater than typically 0.8 but less than orequal to typically 0.95, an inquiry is made as to whether a new noderequires additional power. If so, and a node having a lower priority iscurrently receiving power, the lower priority node has its power supplyreduced and the higher priority node is provided with additional power.

FIG. 20B illustrates a technique useful for full or reducedfunctionality operation with emergency override in involuntary powermanagement in accordance with a preferred embodiment of the presentinvention. The technique of FIG. 20B can be used in the environment ofthe functionality of FIG. 20A.

As seen in FIG. 20B, the system senses an emergency need for additionalpower at a given node. In such a case, the given node is assigned thehighest priority and the functionality of FIG. 20A is applied. Once theemergency situation no longer exists, the priority of the given node isreturned to its usual priority and the functionality of FIG. 20Aoperates accordingly.

FIG. 20C illustrates a technique useful for full or reducedfunctionality operation having queue-controlled priority in involuntarypower management in accordance with a preferred embodiment of thepresent invention. As seen in FIG. 20C, the system initially determinesthe total power available to it as well as the total power that it iscurrently supplying to all nodes. The relationship between the currenttotal power consumption (TPC) to the current total power availability(TPA) is then determined.

If TPC/TPA is less than typically 0.8, additional nodes are suppliedadditional power one-by-one on a queue-controlled, prioritized basis,typically on a first come, first served basis. If TPC/TPA is greaterthan typically 0.95, power to individual nodes is reduced one-by-one ona prioritized basis.

If TPC/TPA is equal to or greater than typically 0.8 but less than orequal to typically 0.95, an inquiry is made as to whether a new noderequires additional power. If so, that node is added to the bottom ofthe queue.

FIG. 20D illustrates a technique useful for full or reducedfunctionality operation having queue-controlled priority in involuntarypower management in accordance with a preferred embodiment of thepresent invention. As seen in FIG. 20D, the system initially determinesthe total power available to it as well as the total power that it iscurrently supplying to all nodes. The relationship between the currenttotal power consumption (TPC) to the current total power availability(TPA) is then determined.

If TPC/TPA is less than typically 0.8, additional nodes are suppliedadditional power one-by-one on a time-sharing, prioritized basis,typically on a basis that the node having the longest duration of use iscut off first. If TPC/TPA is greater than typically 0.95, power toindividual nodes is disconnected one-by-one on a prioritized basis.

If TPC/TPA is equal to or greater than typically 0.8 but less than orequal to typically 0.95, an inquiry is made as to whether a new noderequires additional power. If so, and a node having a lower priority, inthe sense that it has been receiving power for a longer time, which isabove a predetermined minimum time, is currently receiving full power,the lower priority node has its power supply reduced and the higherpriority node is provided with additional power.

Reference is now made to FIGS. 21A, 21B, 21C and 21D are generalizedflowcharts each illustrating one possible mechanism for node initiatedsleep mode operation in a voluntary power management step in theflowchart of FIG. 16.

FIG. 21A illustrates a situation wherein a node operates in a sleep modeas the result of lack of activity for at least a predetermined amount oftime. As seen in FIG. 21A, the time duration TD1 since the last activityof the node is measured. If TD1 exceeds typically a few seconds orminutes, in the absence of a user or system input contraindicating sleepmode operation, the node then operates in a sleep mode, which normallyinvolves substantially reduced power requirements.

FIG. 21B illustrates a situation wherein a node operates in a sleep modeas the result of lack of communication for at least a predeterminedamount of time. As seen in FIG. 21B, the time duration TD2 since thelast communication of the node is measured. If TD2 exceeds typically afew seconds or minutes, in the absence of a user or system inputcontraindicating sleep mode operation, the node then operates in a sleepmode, which normally involves substantially reduced power requirements.

FIG. 21C illustrates a situation wherein a node operates in a sleep modein response to clock control, such that the node is active within aperiodically occurring time slot, absent an input from the system or theuser. As seen in FIG. 21C, the time slots are defined as times TD3 whilethe remaining time is defined as TD4. The node determines whether it iscurrently within the time slot TD3. If not, i.e. during times TD4, itoperates in the sleep mode.

FIG. 21D illustrates a situation wherein a node operates in a sleep modeas the result of a sensed fault condition. As seen in FIG. 21D, the nodeperiodically performs a self-test. The self test may be, for example, anattempt to communicate with the hub. If the node passes the test, itoperates normally. If the node fails the test, it operates in the sleepmode.

Reference is now made to FIGS. 22A, 22B, 22C and 22D, which aregeneralized flowcharts each illustrating one possible mechanism for hubinitiated sleep mode operation in a voluntary power management step inthe flowchart of FIG. 16.

FIG. 22A illustrates a situation wherein a node operates in a sleep modeas the result of lack of activity for at least a predetermined amount oftime. As seen in FIG. 22A, the time duration TD1 since the last activityof the node as sensed by the hub is measured. If TD1 exceeds typically afew seconds or minutes, in the absence of a user or system inputcontraindicating sleep mode operation, the node then operates in a sleepmode, which normally involves substantially reduced power requirements.

FIG. 22B illustrates a situation wherein a node operates in a sleep modeas the result of lack of communication for at least a predeterminedamount of time. As seen in FIG. 22B, the time duration TD2 since thelast communication of the node as sensed by the hub is measured. If TD2exceeds typically a few seconds or minutes, in the absence of a user orsystem input contraindicating sleep mode operation, the node thenoperates in a sleep mode, which normally involves substantially reducedpower requirements.

FIG. 22C illustrates a situation wherein a node operates in a sleep modein response to clock control from the hub, such that the node is activewithin a periodically occurring time slot, absent an input from thesystem or the user. As seen in FIG. 22C, the time slots are defined astimes TD3 while the remaining time is defined as TD4. The nodedetermines whether it is currently within the time slot TD3. If not,i.e. during times TD4, it operates in the sleep mode.

FIG. 22D illustrates a situation wherein a node operates in a sleep modeas the result of a fault condition sensed by the hub. As seen in FIG.22D, the hub periodically performs a test of the node. The self test maybe, for example, an attempt to communicate with the hub. If the nodepasses the test, it operates normally. If the node fails the test, itoperates in the sleep mode.

Reference is now made to FIGS. 23A, 23B, 23C and 23D, which aregeneralized flowcharts each illustrating one possible mechanism for fullor no functionality operation in a voluntary power management step inthe flowchart of FIG. 16.

FIG. 23A illustrates a basic technique useful for full or nofunctionality operation in voluntary power management in accordance witha preferred embodiment of the present invention. As seen in FIG. 23A,the system initially determines the total power allocated to it as wellas the total power that it is currently supplying to all nodes. Therelationship between the current total power consumption (TPC) to thecurrent total power allocation (TPL) is then determined.

If TPC/TPL is less than typically 0.8, additional nodes are suppliedfull power one-by-one on a prioritized basis. If TPC/TPL is greater thantypically 0.95, power to individual nodes is disconnected one-by-one ona prioritized basis.

If TPC/TPL is equal to or greater than typically 0.8 but less than orequal to typically 0.95, an inquiry is made as to whether a new noderequires power. If so, and a node having a lower priority is currentlyreceiving power, the lower priority node is disconnected from power andthe higher priority node is connected to power.

FIG. 23B illustrates a technique useful for full or no functionalityoperation with emergency override in voluntary power management inaccordance with a preferred embodiment of the present invention. Thetechnique of FIG. 23B can be used in the environment of thefunctionality of FIG. 23A.

As seen in FIG. 23B, the system senses an emergency need for power at agiven node. In such a case, the given node is assigned the highestpriority and the functionality of FIG. 23A is applied. Once theemergency situation no longer exists, the priority of the given node isreturned to its usual priority and the functionality of FIG. 23Aoperates accordingly.

FIG. 23C illustrates a technique useful for full or no functionalityoperation having queue-controlled priority in voluntary power managementin accordance with a preferred embodiment of the present invention. Asseen in FIG. 23C, the system initially determines the total powerallocated to it as well as the total power that it is currentlysupplying to all nodes. The relationship between the current total powerconsumption (TPC) to the current total power allocation (TPL) is thendetermined.

If TPC/TPL is less than typically 0.8, additional nodes are suppliedfull power one-by-one on a queue-controlled, prioritized basis,typically on a first come, first served basis. If TPC/TPL is greaterthan typically 0.95, power to individual nodes is disconnectedone-by-one on a prioritized basis.

If TPC/TPL is equal to or greater than typically 0.8 but less than orequal to typically 0.95, an inquiry is made as to whether a new noderequires power. If so, that node is added to the bottom of the queue.

FIG. 23D illustrates a technique useful for full or no functionalityoperation having queue-controlled priority in voluntary power managementin accordance with a preferred embodiment of the present invention. Asseen in FIG. 23D, the system initially determines the total powerallocated to it as well as the total power that it is currentlysupplying to all nodes. The relationship between the current total powerconsumption (TPC) to the current total power allocation (TPL) is thendetermined.

If TPC/TPL is less than typically 0.8, additional nodes are suppliedfull power one-by-one on a time-sharing, prioritized basis, typically ona basis that the node having the longest duration of use is cut offfirst. If TPC/TPL is greater than typically 0.95, power to individualnodes is disconnected one-by-one on a prioritized basis.

If TPC/TPL is equal to or greater than typically 0.8 but less than orequal to typically 0.95, an inquiry is made as to whether a new noderequires power. If so, and a node having a lower priority, in the sensethat it has been receiving power for a longer time, which is above apredetermined minimum time, is currently receiving power, the lowerpriority node is disconnected from power and the higher priority node isconnected to power.

It is appreciated that normally it is desirable that the node beinformed in advance in a change in the power to be supplied thereto.This may be accomplished by signally along the communications cabling ina usual data transmission mode or in any other suitable mode.

Reference is now made to FIGS. 24A, 24B, 24C and 24D, which aregeneralized flowcharts each illustrating one possible mechanism for fullor reduced functionality operation in a voluntary power management stepin the flowchart of FIG. 16.

FIG. 24A illustrates a basic technique useful for full or reducedfunctionality operation in voluntary power management in accordance witha preferred embodiment of the present invention. As seen in FIG. 24A,the system initially determines the total power allocated to it as wellas the total power that it is currently supplying to all nodes. Therelationship between the current total power consumption (TPC) to thecurrent total power allocation (TPL) is then determined.

If TPC/TPL is less than typically 0.8, additional nodes are suppliedfull power one-by-one on a prioritized basis. If TPC/TPL is greater thantypically 0.95, power to individual nodes is reduced one-by-one on aprioritized basis.

If TPC/TPL is equal to or greater than typically 0.8 but less than orequal to typically 0.95, an inquiry is made as to whether a new noderequires additional power. If so, and a node having a lower priority iscurrently receiving power, the lower priority node has its power supplyreduced and the higher priority node is provided with additional power.

FIG. 24B illustrates a technique useful for full or reducedfunctionality operation with emergency override in voluntary powermanagement in accordance with a preferred embodiment of the presentinvention. The technique of FIG. 24B can be used in the environment ofthe functionality of FIG. 24A.

As seen in FIG. 24B, the system senses an emergency need for additionalpower at a given node. In such a case, the given node is assigned thehighest priority and the functionality of FIG. 24A is applied. Once theemergency situation no longer exists, the priority of the given node isreturned to its usual priority and the functionality of FIG. 24Aoperates accordingly.

FIG. 24C illustrates a technique useful for full or reducedfunctionality operation having queue-controlled priority in voluntarypower management in accordance with a preferred embodiment of thepresent invention. As seen in FIG. 24C, the system initially determinesthe total power allocated to it as well as the total power that it iscurrently supplying to all nodes. The relationship between the currenttotal power consumption (TPC) to the current total power allocation(TPL) is then determined.

If TPC/TPL is less than typically 0.8, additional nodes are suppliedadditional power one-by-one on a queue-controlled, prioritized basis,typically on a first come, first served basis. If TPC/TPL is greaterthan typically 0.95, power to individual nodes is reduced one-by-one ona prioritized basis.

If TPC/TPL is equal to or greater than typically 0.8 but less than orequal to typically 0.95, an inquiry is made as to whether a new noderequires additional power. If so, that node is added to the bottom ofthe queue.

FIG. 24D illustrates a technique useful for full or additionalfunctionality operation having queue-controlled priority in voluntarypower management in accordance with a preferred embodiment of thepresent invention. As seen in FIG. 24D, the system initially determinesthe total power allocated to it as well as the total power that it iscurrently supplying to all nodes. The relationship between the currenttotal power consumption (TPC) to the current total power allocation(TPL) is then determined.

If TPC/TPL is less than typically 0.8, additional nodes are suppliedadditional power one-by-one on a time-sharing, prioritized basis,typically on a basis that the node having the longest duration of use iscut off first. If TPC/TPL is greater than typically 0.95, power toindividual nodes is disconnected one-by-one on a prioritized basis.

If TPC/TPL is equal to or greater than typically 0.8 but less than orequal to typically 0.95, an inquiry is made as to whether a new noderequires additional power. If so, and a node having a lower priority, inthe sense that it has been receiving power for a longer time, which isabove a predetermined minimum time, is currently receiving full power,the lower priority node has its power supply reduced and the higherpriority node is provided with additional power.

It will be appreciated by persons skilled in the art that the presentinvention is not limited by what has been particularly shown anddescribed hereinabove. Rather the scope of the present inventionincludes both combinations and sub-combinations of various featuresdescribed hereinabove as well as modifications and variations thereofwhich would occur to persons skilled in the art and which are not in theprior art.

1. A power supply subsystem for providing electrical power to a localarea network node over communication cabling, the power supply subsystemcomprising: a power management and control unit; current limitingcircuitry responsive to said power management and control unit toprovide a current limited output; voltage measurement means; and atleast one of a combiner and a power supply interface operative to couplesaid current limited output to the communication cabling; said powermanagement and control unit being further operative to: measure,utilizing said voltage measuring means at three pre-determinedintervals, a voltage developed in accordance with said coupled currentlimited output; and determine, as a consequence of said measured voltagewhether characteristics of the node allow it to receive power over thecommunication cabling.
 2. A power supply subsystem according to claim 1,wherein said voltage measuring means is operative to measure the voltageat the output of said current limiting circuitry.
 3. A power supplysubsystem according to claim 1, wherein said voltage measuring means isoperative to measure the voltage supplied to the communication cabling.4. A power supply subsystem according to claim 1, wherein said powermanagement and control unit is further operable, prior to said couplingsaid current limited output to the communication cabling, to measure,utilizing said voltage measuring means, a pre-existing voltage presentacross a line associated with the communication cabling.
 5. A powersupply subsystem according to claim 4, wherein in the event that saidmeasured pre-existing voltage exceeds a predetermined threshold, saidpower management and control unit is further operable to classify theline as externally voltage fed.
 6. A power supply subsystem according toclaim 5, wherein said power management and control unit is operative tocouple said current limited output to the communication cabling only inthe event that the line is not classified as externally voltage fed. 7.A power supply subsystem according to claim 1, wherein said powermanagement and control unit further determines the status of the localarea network node for which power is to be provided as a consequence ofsaid measured voltage, said status comprising one of a short circuitcondition, a no load condition, a network interface card load conditionand a power over LAN load condition.
 8. A power supply subsystemaccording to claim 7, wherein said power management and control unit isfurther operable to report said status to a network workstation.
 9. Amethod for supplying power to a local area network node overcommunication cabling, the method comprising: injecting current-limitedcurrent into communication cabling connected to the local area networknode; measuring a voltage developed in accordance with said injectedcurrent limited current across said communication cabling at threepre-determined intervals; and determining, as a consequence of saidmeasured voltage at said three pre-determined intervals whethercharacteristics of the local area network node allow it to receive powerover the communication cabling.
 10. A method according to claim 9,wherein said measuring is accomplished at the output of acurrent-limited supplying circuitry, said current-limited supplyingcircuitry supplying said injected current-limited current.
 11. A methodaccording to claim 9, wherein said measuring is accomplished across aline associated with the communication cabling.
 12. A method accordingto claim 9, further comprising prior to said injecting, measuring apre-existing voltage across a line associated with the communicationcabling.
 13. A method according to claim 12, further comprising: in theevent said measured pre-existing voltage exceeds a predeterminedthreshold, classifying the line associated with the communicationcabling as externally voltage fed.
 14. A method according to claim 13,wherein said injecting is performed only in the event that said measuredpre-existing voltage does not exceed said predetermined threshold.
 15. Amethod according to claim 9, further comprising determining a status ofthe local area network node for which power is to be provided over thecommunication cabling, said status comprising one of a short circuitcondition, a no load condition, a network interface card load conditionand a power over LAN load condition.
 16. A method according to claim 15,wherein said determining a status of the local area network node is aconsequence of said measured voltage.
 17. A method according to claim15, further comprising reporting said determined status to a networkworkstation.
 18. A local area network providing power over communicationcabling comprising: a LAN switch; a plurality of local area networknodes; communication cabling enabling data communication between saidLAN switch and said plurality of local area network nodes; and a powersupply subsystem, said power supply subsystem comprising: a powermanagement and control unit; current limiting circuitry responsive tosaid power management and control unit to supply a current limitedoutput; voltage measurement means; and at least one of a combiner and apower supply interface operative to couple said current limited outputto said communication cabling, said power management and control unitbeing operative to: measure, utilizing said voltage measuring means atthree intervals, a voltage developed in accordance with said coupledprogrammable current limited output; and determine, as a consequence ofsaid measured voltage whether characteristics of at least one of saidplurality of local area network nodes allow it to receive power oversaid communication cabling.
 19. A local area network according to claim18, wherein said voltage measuring means is operative to measure thevoltage at the output of said programmable current limiting circuitry.20. A local area network according to claim 18, wherein said voltagemeasuring means is operative to measure the voltage supplied to saidcommunication cabling.
 21. A local area network according to claim 18,wherein said power management and control unit is further operable,prior to said coupling of said current limited output to saidcommunication cabling, to measure utilizing said voltage measuringmeans, a pre-existing voltage present across a line associated with saidcommunication cabling.
 22. A local area network according to claim 21,wherein in the event that said measured pre-existing voltage exceeds apredetermined threshold, said power management and control unit isfurther operable to classify said line as externally voltage fed.
 23. Alocal area network according to claim 22, wherein said power managementand control unit is operative to couple said current limited output tosaid communication cabling only in the event that said line is notclassified as externally voltage fed.
 24. A local area network accordingto claim 18, wherein said power management and control unit furtherdetermines the status of said at least one of said plurality of localarea network nodes for which power is to be provided, said statuscomprising one of a short circuit condition, a no load condition, anetwork interface card load condition and a power over LAN loadcondition.
 25. A local area network according to claim 24, wherein saiddetermined status if a consequence of said measured voltage.
 26. A localarea network according to claim 24, further comprising a networkworkstation, said power management and control unit reporting saidstatus to said network workstation.
 27. A local area network accordingto claim 18, wherein said power supply subsystem and said LAN switch arelocated in a hub.
 28. A local area network according to claim 18,wherein said power supply subsystem is located between said LAN switchand said at least one of said plurality of local area network nodes. 29.A local area network according to claim 18, wherein said power supplysubsystem is located between said LAN switch and said plurality ofnetwork nodes, said communication cabling connecting said LAN switch andsaid plurality of network nodes via said power supply subsystem.
 30. Apower supply subsystem for providing electrical power to a local areanetwork node over communication cabling, the power supply subsystemcomprising: a power management and control unit; current limitingcircuitry responsive to said power management and control unit to supplya current limited output; voltage measurement means; at least one of acombiner and a power supply interface operative to couple said currentlimiting output to the communication cabling; said power management andcontrol unit being operative to: measure, utilizing said voltagemeasuring means at three pre-determined intervals, a voltage developedin accordance with said coupled current limited output, said voltagebeing measured across a line associated with the communication cabling;determine, as a consequence of said measured voltage at said threepre-determined intervals whether characteristics of the node allow it toreceive power over the communication cabling; and in the event that saidcharacteristics of the node allow it to receive power over thecommunication cabling, provide said programmable current limited outputvia said at least one of a combiner and a power supply interface overthe communication cabling to the node.